Method and apparatus for correcting gate bias for diode-connected transistors

Abstract

The present application discloses a method, system, and apparatus for correcting gate bias for a diode-connected transistor. An example system includes: a first resistor (110) including a first resistor terminal and a second resistor terminal; a second resistor (120) including a first resistor terminal and a second resistor terminal; a first transistor (102) including a current terminal (106) and a gate terminal (104), the current terminal (106) of the first transistor (102) being coupled to the first resistor terminal of the first resistor (110), and the gate terminal (104) of the first transistor (102) being coupled to the second resistor terminal of the first resistor (110); and a second transistor (112) including a first current terminal (116) and a second current terminal (118), the first current terminal (116) of the second transistor (112) being coupled to the gate terminal (104) of the first transistor (102), and the second current terminal (118) of the second transistor (112) being coupled to the first current terminal of the second resistor (120).

Description

[0001] Related applications

[0002] This patent claims the benefit of U.S. Provisional Patent Application Serial No. 62 / 775,656, filed on December 5, 2018. U.S. Provisional Patent Application Serial No. 62 / 775,656 is hereby incorporated by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to transistors, and more particularly to methods and apparatus for correcting gate bias for diode-connected transistors. Background Art

[0004] A transistor such as a metal oxide semiconductor field effect transistor (MOSFET) can be used as a switch. Such a MOSFET can be turned on (e.g., enabled) and off (e.g., disabled) based on a voltage applied to the gate terminal of the MOSFET. In some examples, the terminals of the MOSFET can be connected to utilize the switching operation of the MOSFET so that the MOSFET acts as a diode (e.g., by coupling the drain terminal of the MOSFET to the gate terminal of the MOSFET). In this way, the MOSFET acts like a diode, allowing current to flow from the drain terminal to the source terminal, but preventing current from flowing from the source terminal to the drain terminal. Therefore, the MOSFET can be used to provide reverse current protection in a circuit. Summary of the Invention

[0005] Certain examples disclosed herein correct gate bias for diode-connected transistors. An example system includes: a first resistor including a first resistor terminal and a second resistor terminal; a second resistor including a first resistor terminal and a second resistor terminal; a first transistor including a current terminal and a gate terminal, the current terminal of the first transistor being coupled to the first resistor terminal of the first resistor and the gate terminal of the first transistor being coupled to the second resistor terminal of the first resistor; and a second transistor including a first current terminal and a second current terminal, the first current terminal of the second transistor being coupled to the gate terminal of the first transistor and the second current terminal of the second transistor being coupled to the first current terminal of the second resistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 An example circuit for correcting the gate bias for an example transistor is shown.

[0007] Figure 2 shows that when the transistor operates in enhancement mode Figure 1 Operation of the example circuit.

[0008] Figure 3shows that when the transistor operates in depletion mode Figure 1 Operation of the example circuit.

[0009] Figures 4A to 4C An alternative example circuit for correcting the gate bias for an example transistor is shown.

[0010] Figure 5 An example diode-connected transistor is shown.

[0011] Figure 6A Yes Figure 1 and / or the example circuit of Figure 4 to Figure 5 Example of a temperature versus time timing diagram for a diode-connected transistor.

[0012] Figure 6B Yes Figure 1 and / or the example circuit of Figure 4 to Figure 5 An example timing diagram of the threshold voltage versus time for a diode-connected transistor.

[0013] Figure 6C It is a combination Figure 6A-6B The increased temperature and decreased voltage thresholds are indicated by Figure 5 An example timing diagram of the amount of reverse current in a diode-connected transistor versus time.

[0014] Figure 6D It is a combination Figure 6A-6B The increased temperature and decreased voltage thresholds are indicated by Figure 1 and / or a timing diagram of reverse current amount versus time in the example circuit of FIG. 4 .

[0015] Figure 7 is realized Figure 1 Example circuitry for an example Type-C USB integrated circuit (IC) system.

[0016] The drawings are not drawn to scale. Wherever possible, the same reference numbers will be used throughout the drawings and accompanying written description to refer to the same or like parts.

[0017] Descriptors such as "first," "second," and "third" are used herein when identifying multiple elements or components that can be referenced separately. Unless otherwise specified or understood based on their contextual usage, such descriptors are not intended to confer any meaning of priority, physical order, arrangement in a list, or chronological order, but are merely used as labels to reference multiple elements or components separately for ease of understanding the disclosed examples. In some examples, the descriptor "first" may be used to refer to an element in the detailed description, while a different descriptor such as "second" or "third" may be used to reference the same element in the claims. It should be understood that in such cases, such descriptors are used merely for ease of reference to multiple elements or components. DETAILED DESCRIPTION

[0018] A diode-connected transistor is a transistor that includes terminals connected in a circuit so that the transistor functions as a two-terminal rectifier device, such as a diode. For example, an n-channel MOSFET can be configured to function as a diode when the gate terminal is coupled to the drain terminal. A diode-connected transistor allows current to flow in a first direction (e.g., from the transistor's first current terminal (drain) to the transistor's second current terminal (source)) and prevents current (e.g., reverse current) from flowing in a second direction opposite to the first direction (e.g., from the second current terminal to the first current terminal). In this manner (e.g., because the drain terminal is connected to the source terminal), if the voltage at the drain terminal (Vd) of the n-channel MOSFET (e.g., which is the same as the voltage at the gate terminal) is a threshold voltage (Vt, also known as a forward voltage drop) higher than the voltage at the source terminal (Vs) of the n-channel MOSFET, the MOSFET is enabled (e.g., because Vgs>Vt, where Vgs is Vg-Vs). When the MOSFET is enabled, current can flow from the MOSFET's first current terminal to the MOSFET's second current terminal. Therefore, like a forward-biased diode, when the voltage at the first current terminal of the MOSFET (e.g., corresponding to the anode terminal of the forward-biased diode) is higher than the threshold voltage, current flows from the first current terminal of the MOSFET to the second current terminal (e.g., corresponding to the cathode terminal of the forward-biased diode).

[0019] However, if the voltage at the first current terminal is lower than the threshold voltage and higher than the voltage at the second current terminal, the MOSFET is disabled (e.g., because Vgs < Vt). When the MOSFET is disabled, current (e.g., reverse current) is prevented from flowing from the second terminal of the MOSFET to the first terminal of the MOSFET. Thus, like a reverse-biased diode, when the voltage at the first current terminal of the MOSFET (e.g., corresponding to the anode terminal of the diode) is lower than the threshold voltage, the flow of reverse current from the second current terminal of the MOSFET (e.g., corresponding to the cathode terminal of the diode) to the first current terminal of the MOSFET is blocked. The threshold voltage of the MOSFET is based on the characteristics of the MOSFET (e.g., the flat-band voltage of the MOSFET, the volume ratio of the MOSFET, and the voltage across the oxide of the MOSFET due to depletion-layer charge).

[0020] One advantage of using a diode-connected transistor is that some diode-connected transistors (e.g., depending on the threshold voltage of the transistor) have a lower forward voltage drop than conventional diodes. The forward voltage drop is the maximum value of the voltage difference between the diode terminals (e.g., the maximum voltage difference between the current terminals of a diode-connected MOSFET) required for the diode or diode-connected MOSFET to conduct current (e.g., allow current to flow from the first terminal to the second terminal). An ideal diode has a forward voltage drop of 0V. However, in practice, a simple diode has a forward voltage drop of several hundred millivolts. Some devices can be made to operate like a diode with a voltage drop of only a few millivolts, but such diode-based devices require hundreds of components. Thus, such diodes are large, expensive, and complex. On the other hand, the forward voltage drop of a diode-connected transistor is the threshold voltage of the transistor, which is typically on the order of several hundred millivolts to a few millivolts. Thus, a single diode-connected transistor with a small threshold voltage can be used as a diode with a small forward voltage drop.

[0021] Conventionally, diode-connected transistors have been configured to operate when the transistor operates in enhancement mode rather than depletion mode. In enhancement mode, the transistor is turned on (e.g., enabled) when the gate-source voltage (Vgs) is greater than the threshold voltage (Vt) of the transistor, and is turned off (e.g., disabled) when Vgs is less than Vt. In depletion mode, the transistor is turned on (e.g., enabled) when the gate-source voltage (Vgs) is greater than the threshold voltage (Vt) of the transistor, and is turned off (e.g., disabled) when Vgs is less than Vt. Therefore, when a diode-connected transistor operates in depletion mode, the transistor is turned on when the voltage at the source terminal is higher than the voltage at the drain terminal, thereby allowing reverse current to flow from the source terminal to the drain terminal because the functional Vgs (e.g., 0V) is greater than the depletion Vt. Therefore, since reverse current is not blocked, depletion-type transistors are not conventionally used to implement diode-connected transistors.

[0022] One problem with implementing a diode-connected transistor with a low threshold voltage is the manufacturing variations that create such transistors. These manufacturing variations lead to variations in the threshold voltage of the transistors. Thus, if a transistor with a threshold voltage of 100 millivolts is desired and the threshold voltage varies by 200 millivolts, the actual threshold voltage of the transistor may range from -100 millivolts to 300 millivolts. When the threshold voltage of a transistor is negative, the transistor cannot operate as an enhancement-mode transistor. Instead, it operates as a depletion-mode transistor.

[0023] When the enhancement-mode transistor is used as a switch, the switch is turned off (e.g., disabled) when the voltage at the gate of the enhancement-mode transistor is low. When the switch is disabled, there is no current path between the first current terminal of the transistor and the second current terminal of the enhancement-mode transistor, thereby preventing current from flowing from the first current terminal to the second current terminal. Conversely, when the voltage at the gate of the enhancement-mode transistor is high, the switch is enabled, and a current path exists between the first current terminal and the second current terminal, thereby allowing current to flow from the first current terminal to the second current terminal.

[0024] When a depletion-mode transistor is used as a switch, the switch is turned on (e.g., enabled) when the voltage at the gate of the enhancement-mode transistor is low. For example, when the voltage at the gate of the enhancement-mode transistor is low, the switch is enabled, and a current path exists between the first current terminal of the transistor and the second current terminal of the enhancement-mode transistor, thereby allowing current to flow from the first current terminal to the second current terminal. Therefore, a diode-connected transistor implemented with a depletion-mode transistor will not operate as a diode because when reverse current flows from the second current terminal of the transistor to the first current terminal of the transistor, the diode-connected transistor will be enabled, thereby allowing reverse current to flow from the source terminal to the drain terminal, rather than blocking reverse current.

[0025] In addition, temperature affects the threshold voltage of a transistor. Therefore, a low threshold voltage transistor may initially function as an enhancement mode transistor, but as the temperature of the diode increases, the threshold voltage decreases. Therefore, some low threshold voltage transistors may change from enhancement mode to depletion mode depending on the temperature.

[0026] The examples disclosed herein describe a correction gate bias circuit coupled to a diode-connected transistor. The correction gate bias circuit ensures that the diode-connected transistor operates as a diode regardless of whether the transistor is an enhancement mode transistor or a depletion mode transistor. In this way, a low threshold voltage transistor corresponding to a low forward voltage drop can be used to operate as a diode without having to worry about the effects of threshold voltage tolerance and / or the effects of temperature on the threshold voltage. The exemplary diode-based circuit disclosed herein (e.g., a correction gate bias with a diode-connected transistor) can be used in any circuit and / or system in which a diode can be implemented (e.g., providing reverse current blocking between two components of a system). For example, a diode-based circuit can be used to provide reverse current blocking in a USB pin (e.g., a Type C CC pin pull-up circuit), a gate driver in a power converter, and the like.

[0027] Some field effect transistors include two gate terminals (e.g., a front terminal and a back terminal) and two current terminals (e.g., a source terminal and a drain terminal). In such an example, the gate terminal can be structurally defined, while the current terminal can be functionally (electrically) defined. For an n-channel device, a positive channel current flows from the drain terminal to the source terminal, and the drain voltage is higher than the source voltage. For a p-channel device, a positive channel current flows from the source terminal to the drain terminal, and the source voltage is higher than the drain voltage. Therefore, in such an example, the source terminal and the drain terminal are a function of the operating conditions of the transistor and can be switched as these conditions change.

[0028] Even though the field-effect transistor drain and source terminals can be functionally (electrically) defined, field-effect transistor symbols are typically drawn to identify the source and drain terminals. In asymmetric transistors, the symbol can convey the preferred source and drain terminals. In addition, most circuits have some operating conditions under which the functional (electrical) source and / or drain terminals mostly match the drawn (symbolic) source / drain terminals. Therefore, using symbols with identified source and / or drain terminals can help understand circuit diagrams. However, circuit operating conditions may mean that the functional (electrical) source / drain terminals will be opposite to the drawn (symbolic) source / drain terminals.

[0029] With respect to a current source of a transistor, a current terminal is used herein to refer to the source terminal and / or drain terminal of the transistor. The source terminal and drain terminal of a transistor can be the symbolic (referred to herein as “drawn”) source terminal and symbolic drain terminal of the transistor, or can be the electrical (referred to herein as “functional”) drain terminal and electrical source terminal of the transistor. For example, when the symbolic drain terminal of the transistor is coupled to an input node and the symbolic source terminal of the transistor is coupled to an output node and the voltage at the input node is less than the voltage at the output node, the symbolic drain terminal acts as an electrical source terminal and the symbolic source terminal acts as an electrical drain terminal. Thus, as used herein, a current terminal of a transistor can correspond to (A) a symbolic drain terminal or an electrical source terminal (e.g., depending on the voltage at the current terminal) or (B) a symbolic source terminal or an electrical drain terminal.

[0030] Figure 1 An example circuit 100 (eg, a corrective gate bias circuit) that corrects a gate bias for an example transistor M1 102 is shown. Figure 1 The example circuit 100 includes an example transistor M1 102. The transistor M1 102 includes an example gate terminal 104, a first example current terminal (e.g., a drain terminal) 106, a second example current terminal (e.g., a source terminal) 108, and an example substrate terminal (e.g., a body terminal) 109. The example circuit 100 also includes example resistors (e.g., R1, R2) 110, 120 and an example transistor (e.g., transistor M2) 112. The example transistor M2 112 includes an example gate terminal 114, a first example current terminal (e.g., a drain terminal) 116, a second example current terminal (e.g., a source terminal) 118, and an example substrate terminal 119. Figure 1In the example shown, example transistors M1 102, M2 112 and example resistors 110, 120 are implemented in the same die. However, the components can be implemented in different dies and / or different packages based on user and / or manufacturer preferences. In any system, such as in a USB pin (e.g., a Type-C CC pin pull-up circuit), in a gate driver, in a power converter, etc., the example circuit 100 can be used to allow current in a first direction and prevent reverse current in a second direction opposite to the first direction. Although the example circuit 100 has nodes coupled to ground, these nodes can be coupled to other nodes of the circuit.

[0031] Although the example current terminal 106 is referred to as a drain terminal and the example current terminal 108 is referred to as a source terminal, when the output voltage is greater than the input voltage, the example current terminal 108 functions as a drain terminal (e.g., an electrical drain terminal) and the example current terminal 106 functions as a source terminal (e.g., an electrical source terminal). Therefore, when the output voltage is greater than the input voltage, the example current terminal 106 can be referred to as an electrical source terminal and the current terminal 108 can be referred to as an electrical drain terminal.

[0032] Figure 1 The example transistor M1 102 is an n-channel field effect transistor (e.g., an n-channel MOSFET, NFET, NMOS, etc.). The example gate terminal 104 of the example transistor M1 102 is coupled to the example resistor 110 (e.g., the second resistor terminal of the resistor 110) and the example first current terminal 116 of the example transistor M2 112. The first current terminal 106 of the example transistor M1 102 is coupled to an input node and the example resistor 110 (e.g., the first resistor terminal of the resistor 110). The input node corresponds to an input voltage (Vin), i.e., the potential at the input node. The example second current terminal 108 is coupled to an output node. The output node can be, for example, a processor or other component. The output node corresponds to an output voltage (Vout), i.e., the potential at the output node. The example substrate terminal 109 of the example transistor M1 102 is coupled to ground (e.g., a node coupled to ground). The example transistor M1 402 is configured as a diode-connected transistor.

[0033] Figure 1Example transistor M1 102 can operate in enhancement mode and / or depletion mode. In some examples, a manufacturer may produce example transistor M1 102 to have a very low threshold voltage and operate in enhancement mode. However, due to tolerances associated with the manufacture of example transistor M1 102, the actual threshold voltage may be negative, thereby operating in depletion mode. In some examples, transistor M1 102 can operate in enhancement mode (e.g., when Vt>0V). However, external factors (e.g., temperature) may change to reduce the threshold voltage to below 0V and accidentally operate in depletion mode (e.g., when Vt<0V). In some examples, a manufacturer may prefer to implement example transistor M1 102 with a depletion diode (e.g., as opposed to a low threshold voltage enhancement diode) to ensure that the lowest forward voltage drop is achieved.

[0034] Figure 1 Example transistor M2 112 is an n-channel MOSFET. The threshold voltage of transistor M2 112 is the same (e.g., equal) and / or substantially similar (e.g., substantially equal) to the threshold voltage of example transistor M1 102, where an acceptable amount of difference between the threshold voltages depends on an acceptable amount of leakage current for circuit 100, a resistance difference between example resistors R1 110 and R2 120, and / or any adjustable characteristics of example circuit 100. In some examples, the greater the difference between the threshold voltages of transistors M1 102 and M2 112 (e.g., when transistor M1 102 has greater depletion than transistor M2 112), the greater the reverse leakage current that will flow from the Vout node to the Vin node (e.g., when Vt > 0V). Therefore, a user and / or manufacturer can select transistor M2 112 to have a particular threshold voltage relative to the threshold voltage of transistor M1 102 based on an acceptable amount of leakage current. An example gate terminal 114 of example transistor M2 112 is coupled to ground. A first current terminal 116 of example transistor M2 112 is coupled to example resistor 110 and gate terminal 104 of example transistor M1 102. A second example current terminal 118 is coupled to ground via example resistor R2 120. For example, second example current terminal 118 is coupled to a first resistor terminal of example resistor R2 120, and a second resistor terminal of example resistor R2 120 is coupled to a ground node. Because example gate terminal 114 and second example current terminal 118 are coupled to ground, example transistor 112 is always turned off (e.g., disabled) when transistor M2 112 operates in enhancement mode and is always turned on (e.g., enabled) when transistor M2 112 operates in depletion mode. An example substrate terminal 119 of example transistor M2 112 is coupled to ground.

[0035] Figure 1Example transistor M2 112 can operate in enhancement mode and / or depletion mode. In some examples, a manufacturer can produce example transistor M2 112 to have a very low threshold voltage and operate in enhancement mode. However, due to tolerances associated with the manufacture of example transistor M2 112, the actual threshold voltage may be negative, thereby operating in depletion mode. In some examples, transistor M2 112 can operate in enhancement mode. However, external factors (e.g., temperature) may change to reduce the threshold voltage to below 0V and accidentally operate in depletion mode.

[0036] Figure 1 The example resistors R1 110, R2 120 have the same (e.g., equal) or substantially similar (e.g., substantially equal) resistances (e.g., based on the tolerances of the resistors). For example, the resistors R1 110, R2 120 can be manufactured in the same manner in the same die to have the same and / or substantially similar resistances. In some examples, the resistors R1 110, R2 120 have similar resistances. For example, if some reverse leakage current is acceptable in a circuit and / or system, the resistances of the two resistors R1 110, R2 120 can be different and still be within an acceptable range for leakage current. Additionally or alternatively, the resistances of the example resistors R1 110, R2 120 can be selected to account for differences between the threshold voltages of the example transistors M1 102, M2 112. In some examples, resistor R1 110 may have a greater resistance than R2 to compensate for other mismatches in the circuit (eg, a voltage threshold mismatch between transistors M1 102 , M2 112 ) to increase the amount of negative compensation that can be applied to the high-side transistor.

[0037] exist Figure 1In the example shown, the threshold voltage of the example transistor M1 102 is the same or substantially similar (based on the tolerances of the transistors) to the threshold voltage of the example transistor M2 112. For example, the transistors M1 102 and M2 112 can be manufactured in the same manner in the same die to have the same and / or substantially similar characteristics. In some examples, the transistors M1 102 and M2 112 have similar threshold voltages. For example, if some reverse leakage current is acceptable in a circuit and / or system, the threshold voltages of the two transistors M1 102 and M2 112 can be different and still be within an acceptable range of leakage current. Because the threshold voltages are the same or substantially similar, the example transistors M1 102 and M2 112 will operate in depletion mode at the same time and in enhancement mode at the same time. In depletion mode, example transistors M1 102, M2 112 create a current mirror, wherein the current through example transistor M2 112 (e.g., the current from example first current terminal 116 to example second current terminal 118) sets the maximum reverse current through example transistor M1 102 to create a Vgs regulation voltage (e.g., by biasing Vg) for example transistor M1 102. As described below in conjunction with Figure 2 and Figure 3 As further described, the example circuit 100 allows the example transistor 102 to operate as a diode regardless of whether the transistor 102 is operating in depletion mode (e.g., threshold voltage below 0V) or in enhancement mode (e.g., threshold voltage above 0V). Advantageously, the manufacturer can select the transistor 102 to have a very low or negative threshold voltage to reduce the forward voltage drop while ensuring diode operation without large, complex, and expensive circuitry. Even if external factors (e.g., temperature) cause the example transistor 102 to adjust from enhancement mode to depletion mode, the example circuit 100 will ensure diode operation in depletion mode, as described below in conjunction with Figure 3 Further described.

[0038] Figure 2 Shown Figure 1 An example circuit 100 is provided for correcting a gate bias of the example transistor M1 102 when the example transistor M1 102 and the example transistor 112 operate in enhancement mode. Figure 2 The example circuit 100 includes Figure 1 An example gate terminal 104 , a first example current terminal (eg, drain terminal) 106 , a second example current terminal (eg, source terminal) 108 , and an example substrate terminal (eg, body terminal) 109 of an example transistor M1 102 . Figure 2 The example circuit 100 also includes Figure 1 Example resistors (eg, R1, R2) 110, 120. Figure 2The example circuit 100 also includes Figure 1 An example gate terminal 114 , a first example current terminal (eg, a drain terminal) 116 , a second example current terminal (eg, a source terminal) 118 , and an example substrate terminal 109 of an example transistor M1 112 . Figure 2 Also included is an example table 200 identifying states of example transistors M1 102 , M2 112 based on an input voltage (V_IN) and an output voltage (V_OUT).

[0039] because Figure 2 The example transistors M1 102 and M2 112 have the same or substantially similar threshold voltages, so when the example transistor M1 102 operates in the enhancement mode (e.g., the threshold voltage of the transistor M1 102 is greater than 0V), the example transistor M2 112 also operates in the enhancement mode (e.g., the threshold voltage of the transistor M2 112 is greater than 0V). Accordingly, since the gate terminal 114 and the second example current terminal 118 of the example transistor M2 112 are grounded, the example transistor M2 112 will be disabled (e.g., turned off) during the enhancement mode operation, as shown in the example table 200. Therefore, no current will flow from the node between the example resistor 110 and the gate terminal 104 of the example transistor M1 102 (e.g., as shown in the example table 200). Figure 2 shown by the dotted line).

[0040] Since the gate terminal 104 of the example transistor M1 102 is coupled to the input voltage (V_IN) via the example resistor 110, the voltage at the gate terminal 104 (e.g., V_G_M1) is equal to the input voltage (V_IN). Additionally, the voltage at the first current terminal 106 is equal to the input voltage, and the voltage at the second current terminal 108 is equal to the output voltage. Thus, when the input voltage is higher than the sum of the threshold voltage (e.g., the threshold voltage of the example transistor M1 102) and the output voltage, the gate-source voltage (Vgs) of the example transistor M1 102 (e.g., the voltage difference between the voltage at the gate terminal 104 and the voltage at the second current terminal 108) will be higher than the threshold voltage of the transistor M1 102. Therefore, as shown in the example table 200, the example transistor M1 102 will be enabled (e.g., turned on), and current (e.g., I_M1) can flow from the first current terminal 106 to the second current terminal 108 in the first direction. However, when the input voltage is lower than the sum of the threshold voltage and the output voltage, the gate-source voltage (Vgs) of the example transistor M1 102 will be lower than the threshold voltage of the transistor M1 102. Therefore, as shown in the example table 200, the example transistor M1 102 will be disabled (e.g., turned off), and the reverse current (e.g., I_R_M1) in the second direction opposite to the first direction will be blocked. Additionally, when the example transistor M1 102 is disabled, the current in the first direction will also be blocked. Thus, in the enhancement mode where Vin < Vout, the example circuit 100 functions as a diode.

[0041] Figure 3 illustrates Figure 1 Example circuit 100, which is used to correct the gate bias of example transistor M1 102 when example transistor M1 102 and example transistor 112 operate in depletion mode. Figure 3 Example circuit 100 of Figure 1 includes the example gate terminal 104 of the example transistor M1 102, the first example current terminal (e.g., drain terminal) 106, the second example current terminal (e.g., source terminal) 108, and the example substrate terminal (e.g., body terminal) 109. Figure 3 Example circuit 100 of Figure 1 also includes example resistors (e.g., R1, R2) 110, 120. Figure 3 Example circuit 100 of Figure 1 also includes the example gate terminal 114 of the example transistor M1 112, the first example current terminal (e.g., drain terminal) 116, the second example current terminal (e.g., source terminal) 118, and the example substrate terminal 109. Figure 3Also included is an example table 300 identifying states of example transistors M1 102 , M2 112 based on an input voltage (V_IN) and an output voltage (V_OUT).

[0042] because Figure 2 The example transistors M1 102 and M2 112 have the same or substantially similar threshold voltages, so when the example transistor M1 102 operates in depletion mode (e.g., the threshold voltage of the transistor M1 102 is less than 0V), the example transistor M2 112 also operates in depletion mode (e.g., the threshold voltage of the transistor M2 112 is less than 0V). Accordingly, since the gate terminal 114 of the example transistor M2 112 is grounded and the voltage at the second example current terminal 118 of the example is not negative, the example transistor M2 112 will be enabled (e.g., turned on) during depletion mode operation, as shown in the example table 200. Therefore, a current (e.g., I_M2) will flow from the first current terminal 116 of the example transistor M2 112 to the second current terminal 118 (e.g., from a node between the example resistor 110 and the gate terminal 104 of the example transistor M1 102 to ground via the example resistor R2 120).

[0043] because Figure 2 Example transistor M2 112 is in depletion mode (eg, Vt<0V), and the drain current of transistor M2 112 in a saturation state corresponds to Vgs-Vt (eg, Id∝(Vgs-Vt) 2 ), so even if Vgs is 0V, the drain current of the example transistor M2 112 is positive, thereby forming a channel in the example transistor M2 112. As current flows from the first current terminal 116 to the second current terminal 118 through the newly formed channel, the voltage at the second current terminal 118 (e.g., the source voltage) rises from 0V to Vgst (e.g., Vgs-Vt), which can be supported by the transistor M2 112. When the resistance of the example resistor R2 120 is large enough, Vgst is almost zero. In this way, the voltage at the second current terminal 118 is approximately equal to the absolute value (abs) of Vt. Since the voltage at the second current terminal 118 is Vt, based on Ohm's law, the current (e.g., I_M2) from the first current terminal 116 to the second current terminal 118 of the example transistor M2 112 is equal to the absolute value of Vt divided by the resistance of R2 120 (e.g., abs(Vt) / R2).

[0044] The current through the example resistor R1 is the same as the current flowing through the example transistor M2 112 (e.g., from the first current terminal 116 to the second current terminal 118 to ground via the resistor R2 120) (e.g., I_M2). Therefore, based on Ohm's law, the voltage drop across the example resistor R1 110 is equal to the product of I_M2 and the resistance of the resistor R1 110 (e.g., (I_M2)(R1)). Since I_M2 is equal to abs(Vt) / R2, the voltage drop across the example resistor R1 110 is equal to the product of (i) the absolute value of Vt and (ii) the quotient of R1 and R2 (e.g., abs(Vt)(R1 / R2)). Thus, the voltage at the gate terminal 104 of the example transistor M1 102 (e.g., V_G_M1) is equal to the input voltage minus the voltage across the example resistor R1 110 (e.g., V_G_M1=V_IN-abs(Vt)(R1 / R2)). As described above, in some examples, the resistances of the example resistors R1 110 and R2 120 are equal or substantially equal. Thus, in such examples, the voltage at the gate terminal 104 of the example transistor M1 102 is equal to the input voltage minus the absolute value of the threshold voltage (e.g., V_IN-abs(Vt)). Thus, the example transistor M2 112 is configured to bias the voltage at the gate terminal of the example transistor M1 102 when in depletion mode by drawing current across the second resistor R2 120. For example, the bias voltage at the gate terminal 104 is the input voltage (e.g., V_IN-abs(Vt)) biased by the threshold voltage.

[0045] As shown in example table 300, during depletion mode of example transistor M1 102, when the input voltage is greater than the output voltage, transistor M1 102 is enabled (e.g., turned on). To enable example transistor M1 102 during depletion mode, Vgs needs to be greater than the threshold voltage. When the input voltage (V_IN) is greater than the output voltage (V_OUT), the source terminal of example transistor M1 102 is the second current terminal 108. Therefore, since Vg of example transistor M1 102 is equal to V_IN-abs(Vt) and Vs of example transistor M1 102 is V OUT, Vgs is equal to V IN-abs(Vt)-V OUT. When the input voltage (V IN) is greater than the output voltage (V_OUT), V_IN-abs(Vt)-V_OUT will always be greater than Vt. Thus, when V_IN is greater than V_OUT, the example transistor M1 102 will be enabled in depletion mode, causing the I_M1 current to flow from the first current terminal 106 to the second current terminal 108 .

[0046] As shown in example table 300, during depletion mode of example transistor M1 102, when the input voltage is less than the output voltage, transistor M1 102 is disabled (e.g., turned off). To disable example transistor M1 102 during depletion mode, Vgs-Vt needs to be less than zero. When the input voltage (V_IN) is less than the output voltage (V_OUT), the first current terminal 106 functions as the source terminal of example transistor M1 102 (e.g., the first current terminal 106 is an electrical source terminal). Therefore, since Vg of example transistor M1 102 is equal to V_IN-abs(Vt) and Vs of example transistor M1 102 is V_IN, Vgs is equal to V_IN-abs(Vt)-V_IN. Therefore, the reverse Vgs (e.g., when first current terminal 106 functions as a source terminal) is equal to -abs(Vt). Accordingly, Vgs-Vt becomes -abs(Vt)-Vt, which is equal to 0V. Thus, when V_IN is less than V_OUT, the example transistor M1 102 will be disabled in depletion mode (e.g., because when Vgs−Vt=0V, Vgs−Vt≤0V), thereby preventing reverse current (I_R_M1) from flowing from the second current terminal 108 to the first current terminal 106. Thus, when the example transistor M1 102 is in depletion mode, the example circuit 100 acts as a diode.

[0047] Figure 4A An alternative example circuit 400 for correcting the gate bias for an example transistor M1 402 is shown. Figure 4A The example circuit 400 includes Figure 1 110, R2 120. The example circuit 400 also includes an example transistor M1 402. The transistor M1 402 includes an example gate terminal 404, a first example current terminal (e.g., a source terminal) 406, a second example current terminal (e.g., a drain terminal) 408, and an example substrate terminal (e.g., a body terminal) 409. The example circuit 400 also includes an example transistor (e.g., a transistor M2) 412. The example transistor M2 412 includes an example gate terminal 414, a first example current terminal (e.g., a source terminal) 416, a second example current terminal (e.g., a drain terminal) 418, and an example substrate terminal 419. Figure 1 In the example shown, example transistors M1 402, M2 412 and example resistors 110, 120 are implemented in the same die. However, the components may be implemented in different dies and / or different packages based on user and / or manufacturer preferences. Although example circuit 400 has nodes coupled to ground, these nodes may be coupled to other nodes of the circuit.

[0048] Figure 4AExample transistor M1 402 is a p-channel field effect transistor (e.g., p-channel MOSFET, PFET, PMOS, etc.). Example gate terminal 404 of example transistor M1 402 is coupled to example resistor 110 and example second current terminal 418 of example transistor M2 412. First example current terminal 406 is coupled to an output node. The output node can be, for example, a processor or other component. The output node corresponds to an output voltage (Vout), i.e., the potential at the output node. Second current terminal 408 of example transistor M1 402 is coupled to an input node and example resistor 110. The input node corresponds to an input voltage (Vin), i.e., the potential at the input node. Example substrate terminal 409 of example transistor M1 402 is coupled to ground. Example transistor M1 402 is configured as a diode-connected transistor.

[0049] Figure 4A Example transistor M1 402 can operate in enhancement mode and / or depletion mode. In some examples, a manufacturer can produce example transistor M1 402 to have a very low absolute threshold voltage (e.g., the absolute value of the threshold voltage is very low) and operate in enhancement mode. However, due to tolerances associated with the manufacture of example transistor M1 402, the actual threshold voltage may be positive, thereby operating in depletion mode. In some examples, transistor M1 402 can operate in enhancement mode (e.g., when Vt < 0V). However, external factors (e.g., temperature) may change to reduce the threshold voltage to above 0V and accidentally operate in depletion mode (e.g., when Vt > 0V).

[0050] Figure 4AExample transistor M2 412 is a p-channel MOSFET. The threshold voltage of transistor M2 412 is the same and / or substantially similar to the threshold voltage of example transistor M1 402. The greater the difference between the threshold voltages of transistors 402 and 412 (e.g., when transistor M1 402 has stronger depletion than transistor M2 412), the greater the reverse leakage current flowing from the Vout node to the Vin node will be. Therefore, a user and / or manufacturer can select transistor M2 412 to have a specific threshold voltage corresponding to the threshold voltage of transistor M1 402 based on an acceptable amount of leakage current. Example gate terminal 414 of example transistor M2 412 is coupled to ground. First example current terminal 416 is coupled to ground via example resistor R2 120. Second current terminal 418 of example transistor M2 412 is coupled to example resistor 110 and gate terminal 404 of example transistor M1 402. Because the example gate terminal 414 and the first example current terminal 416 are both coupled to ground, the example transistor 412 is always turned off (e.g., disabled) when the transistor M2 412 operates in enhancement mode, and is always turned on (e.g., enabled) when the transistor M2 412 operates in depletion mode. An example substrate terminal 419 of the example transistor M2 412 is coupled to ground.

[0051] Figure 4A Example transistor M2 412 can operate in enhancement mode and / or depletion mode. In some examples, a manufacturer can produce example transistor M2 412 to have a very low absolute threshold voltage and operate in enhancement mode. However, due to tolerances associated with the manufacture of example transistor M2 412, the actual threshold voltage may be negative, thereby operating in depletion mode. In some examples, transistor M2 412 can operate in enhancement mode. However, external factors (e.g., temperature) may change to reduce the threshold voltage to below 0V and accidentally operate in depletion mode.

[0052] exist Figure 4AIn the example shown, the threshold voltage of the example transistor M1 402 is the same or substantially similar (based on the tolerances of the transistors) to the threshold voltage of the example transistor M2 412. For example, the transistors M1 402 and M2 412 can be manufactured in the same manner in the same die to have the same and / or substantially similar characteristics. In some examples, the transistors M1 402 and M2 412 have similar threshold voltages. For example, if some reverse leakage current is acceptable in the circuit and / or system, the threshold voltages of the two transistors M1 402 and M2 412 can be different and still be within an acceptable range of leakage current. Because the threshold voltages are the same or substantially similar, the example transistors M1 402 and M2 412 will operate in depletion mode at the same time and will operate in enhancement mode at the same time.

[0053] In enhancement mode, the example transistor M2 412 is turned off (e.g., disabled). Therefore, the voltage at the gate terminal 404 of the example transistor M1 402 is equal to the voltage at the input node. If the voltage at the input node (e.g., the voltage at the second current terminal 408) is less than the voltage at the output node (e.g., the voltage at the first current terminal 406) minus the absolute threshold voltage, the transistor M1 402 is enabled (e.g., turned on), and current flows from the first current terminal 406 to the second current terminal 408. However, if the voltage at the input node (e.g., the voltage at the second current terminal 408) is greater than the voltage at the output node (e.g., the voltage at the first current terminal 406) minus the absolute threshold voltage, the transistor M1 402 is disabled (e.g., turned off), and reverse current from the second current terminal 408 to the first current terminal 406 is blocked.

[0054] In depletion mode, example transistors M1 402, M2 412 create a current mirror, wherein the current through example transistor M2 412 (e.g., the current from example second current terminal 418 to example second current terminal 416) sets the maximum reverse current through example transistor M1 402 to create a Vgs regulation voltage (e.g., by biasing Vg) for example transistor M1 402. Thus, when the voltage at the input node is lower than the voltage at the output node and transistor M1 402 is in depletion mode, example transistor M1 402 is enabled (e.g., turned on) to allow current to flow from first current terminal 406 to second current terminal 408. Additionally, when the voltage at the input node is higher than the voltage at the output node plus a threshold voltage, example transistor M1 402 is disabled (e.g., turned off) to prevent reverse current from second current terminal 408 to first current terminal 406. Thus, the example circuit 400 allows the example transistor M1 402 to operate as a diode regardless of whether the transistor M1 402 is operating in depletion mode (e.g., threshold voltage below 0V) or in enhancement mode (e.g., threshold voltage above 0V). Advantageously, manufacturers can select transistor M1 402 to have a very low or negative threshold voltage to reduce forward voltage drop without requiring large, complex, and expensive circuitry to ensure diode operation. Even if external factors (e.g., temperature) cause the example transistor M1 402 to adjust from enhancement mode to depletion mode, the example circuit 400 will ensure diode operation in depletion mode.

[0055] Figure 4B An alternative example circuit 420 that corrects the gate bias for an example transistor M1 422 is shown. Figure 4B The example circuit 420 includes Figure 1 The example circuit 420 further includes an example transistor M1 422. The transistor M1 422 includes an example gate terminal 424, a first example current terminal (e.g., a source terminal) 426, a second example current terminal (e.g., a drain terminal) 428, and an example substrate terminal (e.g., a body terminal) 429. Figure 4B In the example shown, example transistors M1 402, M2 112 and example resistors 110, 120 are implemented in the same die. However, the components may be implemented in different dies and / or different packages based on user and / or manufacturer preferences. Although example circuit 420 has nodes coupled to ground, these nodes may be coupled to other nodes of the circuit.

[0056] Figure 4B An example of transistor M1 422 with Figure 1 The example transistor M1 102 is configured differently, but operates in the same manner. For example, transistor M1 422 is a vertically flipped NMOS. Thus, the example current terminal 426 is a source terminal, and the example current terminal 428 is a drain terminal. The example substrate terminal 429 is coupled to the example current terminal 426. In this manner, when operating in enhancement mode, the example transistor 422 is turned on (e.g., enabled) when the example input voltage is a threshold voltage higher than the output voltage (e.g., to allow current to flow from the current terminal 426 to the current terminal 428), and is turned off (e.g., disabled) when the input voltage is lower than the output voltage (e.g., to prevent current from flowing from the example current terminal 428 to the example current terminal 426). Additionally, as described above in conjunction with Figure 1-3 As depicted, when the example transistor 422 operates in depletion mode, the example transistor 422 operates as a diode.

[0057] Figure 4C An alternative example circuit 430 that corrects the gate bias for example transistor M1 432 is shown. Figure 4C An example circuit 430 includes Figure 4A 10, R2 120, an example transistor M2 412, an example gate terminal 414, example current terminals 416, 418, and an example substrate terminal 419. The example circuit 430 also includes an example transistor M1 432. The transistor M1 432 includes an example gate terminal 434, a first example current terminal (e.g., a source terminal) 436, a second example current terminal (e.g., a drain terminal) 438, and an example substrate terminal (e.g., a body terminal) 439. Figure 4C In the example shown, example transistors M1 402, M2 412 and example resistors 110, 120 are implemented in the same die. However, the components may be implemented in different dies and / or different packages based on user and / or manufacturer preferences. Although example circuit 430 has nodes coupled to ground, these nodes may be coupled to other nodes of the circuit.

[0058] Figure 4B An example of transistor M1 432 with Figure 4AThe example transistor M1 402 is configured differently but operates in the same manner. For example, transistor M1 432 is a vertically flipped PMOS. Thus, the example current terminal 436 is a drain terminal, and the example current terminal 438 is a source terminal. The example substrate terminal 439 is coupled to the example current terminal 438. In this manner, when operating in enhancement mode, the example transistor 432 is turned on (e.g., enabled) when the example input voltage is a threshold voltage higher than the output voltage (e.g., to allow current to flow from the current terminal 438 to the current terminal 436), and is turned off (e.g., disabled) when the input voltage is lower than the output voltage (e.g., to prevent current from flowing from the example current terminal 436 to the example current terminal 438). Additionally, as described above in conjunction with Figure 4A As depicted, when the example transistor 432 operates in depletion mode, the example transistor 432 operates as a diode.

[0059] Figure 5 An alternative circuit for implementing a diode-connected transistor is shown. Figure 5 A first example diode-connected transistor 500 , a second example diode-connected transistor 502 , and a third example diode-connected transistor 504 are included.

[0060] Figure 5 The first example diode-connected transistor 500 is an NMOS transistor having a gate terminal, a first current terminal (e.g., a drain terminal) coupled to an input voltage node, and a second current terminal (e.g., a source terminal) coupled to an output voltage node. The example diode-connected transistor 500 operates as a diode in enhancement mode. However, in depletion mode, when the voltage at the output terminal is greater than the voltage at the input terminal, the diode-connected transistor 500 cannot prevent reverse current (e.g., current from the second current terminal to the first current terminal).

[0061] Figure 5 The example diode-connected transistor 502 is an alternative configuration of a diode-connected transistor. The example diode-connected transistor 502 is an NMOS transistor having a gate terminal, a second current terminal (e.g., a source terminal) coupled to an input voltage node, and a first current terminal (e.g., a drain terminal) coupled to an output voltage node. Similar to the example diode-connected transistor 502, when the example diode-connected transistor 502 operates in enhancement mode, the example diode-connected transistor 502 functions as a reverse current blocking diode. However, similar to the example diode-connected transistor 502, when the example diode-connected transistor 502 operates in depletion mode, the example diode-connected transistor 502 does not block reverse current.

[0062] Figure 5The example diode-connected transistor 504 includes a voltage source coupled between the gate terminal and the first current terminal (e.g., drain terminal) / input voltage terminal. The voltage source biases Vgs at a fixed voltage to always set it to the worst-case depletion voltage. However, the power supply is a large and expensive component. In addition, Figure 1 4 . Therefore, the example diode-connected transistor 504 will require additional leakage components to reduce leakage current, which increases the cost, complexity and size of the example diode-connected transistor 504. In addition, by using the example diode-connected transistor 504, when the threshold voltage ranges from -0.3V to 0.2V and the voltage source is between 0.35V and 0.4V (e.g., taking into account tolerances), the worst-case forward voltage drop will be in the range of 0.1V to 0.6V. However, by using the example circuits 100, 400, the worst-case forward voltage drop is in the range of 0V to 0.2V, which corresponds to a forward voltage drop improvement of 0.4V.

[0063] Figures 6A-6D 6 shows example timing diagrams 600, 610, 620, 630 when the circuit changes from enhancement mode to depletion mode. Figure 1 The operation of the example circuits 100 and 400 of FIG. 4 is similar to Figure 5 A comparison between the operation of example transistors 500, 502. Figure 6A The example timing diagram 600 illustrates example temperature 605 of the example circuits 100 , 400 and / or transistors 500 , 502 with respect to time. Figure 6B The example timing diagram 610 shows example threshold voltages 615 of transistors 102 , 402 , 500 , 502 with respect to time.

[0064] Figure 6C An example timing diagram 620 shows Figure 5 Example reverse current 625 (eg, current from the source terminal to the drain terminal) of transistors 500 , 502 with respect to time. Figure 6D An example timing diagram 630 shows Figure 1 and / or the example reverse current 635 (eg, current from the source terminal to the drain terminal) of the transistors 102, 402 of FIG. 4 with respect to time. Figure 6A In the illustrated example of -D, the example transistors 102, 402, 500, 502 correspond to the same threshold voltage (Vt), and the output voltage is greater than the input voltage.

[0065] exist Figures 6A-6DIn the example diagram, before time t1, the example transistors 102, 402, 500, 502 have a positive threshold voltage. Therefore, because the output voltage is greater than the input voltage, the transistors 102, 402, 500, 502 are disabled as described above. Therefore, the example reverse current 625, 635 is blocked before time t1 (e.g., the reverse current is equal to 0 amperes (A)). As the example temperature 605 increases, the example threshold voltage 615 begins to decrease.

[0066] At time t1, due to the increase in temperature 605, the threshold voltage 615 becomes a negative voltage. Therefore, the example transistors 102, 402, 500, 502 transition from enhancement mode to depletion mode. As such, at time t1, the example diode-connected transistors 500, 502 are enabled and reverse current flow is prevented, thereby allowing the example reverse current 625 to flow (e.g., from the source to the drain of the example diode-connected transistors 500, 502), as described above in conjunction with Figure 5 As described above, the example reverse current 625 increases at time t1. However, as described above in conjunction with Figure 1 4 , when the example transistor 102 , 402 transitions to depletion mode, the example transistor 102 , 402 continues to block the example reverse current 635 . Therefore, the example reverse current 635 remains at 0V after time t1 .

[0067] Figure 7 is an example system diagram of an example circuit 100 implemented in an example Type-C USB integrated circuit (IC) system 700. The example Type-C USB IC system 700 includes Figure 1-Figure 3 The example circuit 100 includes an example transistor M1 102, an example gate terminal 104, a first example current terminal 106, a second example current terminal 108, and an example substrate terminal 109. The example Type-C USB IC system 700 also includes example transistors (MP1, MP2) 702, 704 configured as an example current mirror 705, an example current reference 706, an example IC power pin 708, and an example CC1 pin 710 of a Type-C USB device. Although Figure 7 The example circuit 100 is used in the example Type-C USB integrated circuit (IC) system 700 to prevent reverse current, but Figures 4A-4C Any of the example circuits 400, 420, 430 may also be used to prevent reverse current.

[0068] exist Figure 7In the example Type-C USB IC system 700, example transistors MP1 702 and MP2 704 are PMOS transistors configured as an example current mirror 705. Thus, a current corresponding to an example current reference 706 is mirrored and output to the example circuit 100. First current terminals (e.g., source terminals) of the example transistors 702 and 704 are coupled to an IC power pin 708 via a power rail terminal of the current mirror 705. A second current terminal (e.g., drain terminal) of the example transistor MP1 702 (e.g., an input terminal of the current mirror 705) is coupled to the example current reference 706, and a second current terminal (e.g., drain terminal) of the example transistor MP2 704 (e.g., an output terminal of the current mirror 705) is coupled to a first example current terminal 106 of the example transistor M1 102 in the example circuit 100. A second example current terminal 108 of the example transistor M1 102 in the circuit 100 is coupled (e.g., directly or via a cable CC line) to a CC1 pin 710 of the Type-C USB device.

[0069] Figure 7 The example transistors 702, 704 and the example reference current source 706 create a Type-C source pull-up resistor used in the Type-C USB specification that sends current to the example CC1 pin 710. However, if the supply rail of the Type-C device is lower than the supply rail of the device coupled to the IC power pin 708, and reverse current is not prevented, undesirable reverse current may flow from the CC1 pin 710 to the IC pin 708. However, as described above in conjunction with Figure 1-3 As described above, example circuit 100 blocks undesirable reverse current flow regardless of whether transistor M1 106 is in depletion mode or enhancement mode. Therefore, transistor M1 106 can be implemented with a very low or negative threshold voltage to produce a low forward voltage drop while still blocking reverse current flow. The lower the voltage drop (e.g., the lower the threshold voltage), the less impact circuit 100 has on the Type-C source's ability to pull up the CC pin to the USB Type-C specification requirements.

[0070] exist Figure 7 In the example shown, resistor R1 110 is coupled to the high voltage rail of the example current mirror 705 / IC power pin 708 to connect to the highest potential in the circuit (e.g., the power rail protected from reverse current by circuit 100). However, the example resistor R1 110 can be coupled to the drain of the example transistor M1 102 (such as in Figure 1 middle).

[0071] As used herein, "include" and "comprising" (and all forms and tenses thereof) are open-ended terms. Thus, whenever a claim employs any form of "include" or "comprising" (e.g., "including," "having," etc.) as a preamble or in any type of claim statement, it should be understood that other elements, terms, etc. may be present without exceeding the scope of the corresponding claim or statement. As used herein, when the phrase "at least" is used as a transition term, such as in the preamble of a claim, it is open-ended in the same manner that the terms "include" and "comprising" are open-ended. When the term "and / or" is used, for example, in a form such as A, B, and / or C, it refers to any combination or subset of A, B, and C, such as (1) only A, (2) only B, (3) only C, (4) A and B, (5) A and C, (6) B and C, and (7) A and B and A and C. As used herein in the context of describing structures, components, items, objects, and / or things, the phrase "at least one of A and B" is intended to refer to implementations that include: (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. Similarly, as used herein in the context of describing structures, components, items, objects, and / or things, the phrase "at least one of A or B" is intended to refer to implementations that include: (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. As used herein in the context of describing the performance or execution of processes, instructions, acts, activities, and / or steps, the phrase "at least one of A and B" is intended to refer to implementations that include: (1) at least one A, (2) at least one B, and (3) at least one A and at least one B. Similarly, as used herein in the context of describing the performance or execution of a process, instruction, action, activity, and / or step, the phrase "at least one of A or B" is intended to refer to embodiments that include: (1) at least one A, (2) at least one B, and (3) at least one A and at least one B.

[0072] Based on the foregoing, it should be understood that example methods, apparatus, and articles for correcting gate bias for diode-connected transistors. The examples disclosed herein ensure that a diode-connected transistor acts as a diode to allow circuit flow in a first direction and prevent reverse current flow in a second direction opposite to the first direction, regardless of whether the diode-connected transistor operates in enhancement mode or depletion mode. In this way, a diode-connected transistor can be produced that has a small (e.g., even negative) threshold voltage corresponding to a small forward voltage drop and has fewer, smaller, and more efficient components. Thus, the examples disclosed herein provide an improvement over previous diode-connected transistors.

[0073] Although certain example methods, apparatus, and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the claims of this patent.

Claims

1. An integrated circuit comprising: input terminals, circuit ground, and output terminals; A first transistor having: a first current terminal coupled to the input terminal; Control terminals; a substrate terminal coupled to the input terminal; and a second current terminal coupled to the output terminal; a first resistor coupled between the input terminal and the control terminal of the first transistor; A second transistor having: a first current terminal coupled to the control terminal of the first transistor; a control terminal coupled to the circuit ground; a substrate terminal coupled to the circuit ground; and a second current terminal; as well as A second resistor is coupled between the second current terminal of the second transistor and circuit ground. 2 . The integrated circuit of claim 1 , wherein the first current terminal of the first transistor is a source, and the second current terminal of the first transistor is a drain. 3 . The integrated circuit of claim 1 , wherein the first current terminal of the second transistor is a drain, and the second current terminal of the second transistor is a source.

4. An integrated circuit comprising: input terminals, circuit ground, and output terminals; A first transistor having: a first current terminal coupled to the input terminal; Control terminals; a substrate terminal coupled to the circuit ground; and a second current terminal coupled to the output terminal; a first resistor coupled between the input terminal and the control terminal of the first transistor; A second transistor having: a first current terminal coupled to the control terminal of the first transistor; a control terminal coupled to the circuit ground; a substrate terminal coupled to the circuit ground; and a second current terminal; as well as A second resistor is coupled between the second current terminal of the second transistor and circuit ground. The integrated circuit of claim 4 , comprising a USB-C Type CC1 pin coupled to the output terminal.

6. The integrated circuit according to claim 4, comprising: a current mirror circuit having an input coupled to the input terminal, having a current source terminal, and having an output coupled to the first current terminal of the first transistor; and A current source has a first terminal coupled to the current source terminal and has a second terminal coupled to the circuit ground.

7. The integrated circuit of claim 6 , wherein the current mirror circuit comprises: A third transistor has a first current terminal coupled to the input terminal, a control terminal coupled to the current source terminal, and a second current terminal coupled to the current source terminal.

8. The integrated circuit of claim 7, wherein the third transistor is a p-channel field effect transistor.

9. The integrated circuit of claim 7 , wherein the current mirror comprises: A fourth transistor has a first current terminal coupled to the input terminal, has a control terminal coupled to the current source terminal, and has a second current terminal coupled to the first current terminal of the first transistor.

10. The integrated circuit of claim 9, wherein the fourth transistor is a p-channel field effect transistor.

11. The integrated circuit of claim 4, wherein the first transistor is an n-channel field effect transistor.

12. The integrated circuit of claim 4, wherein the second transistor is an n-channel field effect transistor.

13. The integrated circuit of claim 4, wherein the first transistor has a first threshold voltage, the second transistor has a second threshold voltage, and the first threshold voltage and the second threshold voltage are substantially similar.

14. The integrated circuit of claim 4, wherein the first transistor has a first threshold voltage, the second transistor has a second threshold voltage, and the first threshold voltage and the second threshold voltage are the same.

15. The integrated circuit of claim 4, wherein the first transistor is a p-channel field effect transistor.

16. The integrated circuit of claim 4, wherein the second transistor is a p-channel field effect transistor. 17 . The integrated circuit of claim 4 , wherein the first current terminal of the first transistor is a drain, and the second current terminal of the first transistor is a source.

18. The integrated circuit of claim 4, wherein the first current terminal of the second transistor is a drain, and the second current terminal of the second transistor is a source.

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