A power amplifier bias circuit based on GaAs HBT technology

Abstract

The present invention discloses a power amplifier bias circuit based on a GaAs HBT process, comprising a temperature compensation unit, a standard current mirror bias unit, and a multi-step temperature coefficient voltage unit. The standard current mirror bias unit includes a replica circuit unit and an output circuit unit, each of which houses a first HBT transistor (HBT1) and a third HBT transistor (HBT3). The multi-step temperature coefficient voltage unit is disposed within the replica circuit unit. The bias circuit provided by the present invention incorporates the multi-step temperature coefficient voltage unit within the replica circuit unit of the standard current mirror bias unit, simplifying the circuit and facilitating on-chip integration. The bias circuit also modifies the current mirror structure, utilizing the current amplification function of transistors to reduce leakage current of the first HBT transistor (HBT1), improve the transmission accuracy between the output bias current and the input reference current, and output a stable bias current.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency chips, and in particular to a power amplifier bias circuit based on a GaAs HBT process. Background Art

[0002] In the design of GaAs HBT PA (Heterojunction Bipolar Transistor Power Amplifier), with the continuous development of 5G PA, while reducing the chip area, it also causes self-heating effect inside the chip, resulting in severe temperature drift.

[0003] At present, there are different types of on-chip circuit structures to address this problem. For example, the Chinese patent "A power amplifier chip bias circuit based on GaAs HBT process" with publication number CN111665898A, which was published on September 15, 2020, first uses diodes to automatically compensate for temperature drift, and then connects several HBT tubes in series to replace traditional resistors. A bias voltage is drawn out from each HBT tube to achieve multi-order positive temperature coefficient voltage output, and then this voltage is further converted through a current mirror and a positive temperature coefficient second resistor to provide a bias current for temperature drift suppression for the power amplifier chip.

[0004] However, this circuit still has the following problems:

[0005] 1. The temperature compensation circuit and bias circuit are arranged separately, and the external reference voltage can only control the working state of the current mirror. The circuit is complex, the power consumption is high and it is not conducive to on-chip integration.

[0006] 2. Due to the base shunt inside the current mirror and the self-heating effect of the HBT, the transmission accuracy of the reference current and the output bias current is not high, which is not conducive to the output of stable current.

[0007] Therefore, there is an urgent need for an on-chip temperature compensation bias circuit with high integration, small area and power consumption, and high transmission accuracy to meet the working requirements of RF chips. Summary of the Invention

[0008] The present invention provides a power amplifier bias circuit based on GaAs HBT technology, which can at least solve some of the problems mentioned in the background technology.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a power amplifier bias circuit based on a GaAs HBT process, comprising a temperature compensation unit, a standard current mirror bias unit, and a multi-stage temperature coefficient voltage unit, wherein the standard current mirror bias unit comprises a replica circuit unit and an output circuit unit, wherein a first HBT tube HBT1 and a third HBT tube HBT3 are respectively disposed in the replica circuit unit and the output circuit unit; the multi-stage temperature coefficient voltage unit is disposed in the replica circuit unit and comprises a plurality of HBT tubes HBTA connected in series with collectors and bases connected, wherein the emitter output terminal of the last HBT tube HBTA is connected to the collector of the first HBT tube HBT1, and the emitter of the first HBT tube HBT1 is grounded;

[0010] The temperature compensation unit is provided with a power supply Vc, which outputs a reference current which passes through the HBT tubes HBTA connected in series to the first HBT tube HBT1 and then to ground, and another which passes through the third HBT tube HBT3 and then outputs a bias current.

[0011] Furthermore, the temperature compensation unit includes a diode and a resistor R1, the diode is connected between the power supply and the resistor, the current at the power supply end passes through the diode and the resistor and is grounded, and the other current passes through the diode and is connected to the standard current mirror bias unit, which is used to provide a reference current for the standard current mirror bias unit.

[0012] Furthermore, the replica circuit unit further includes a resistor R2, one end of which serves as a current input of the replica circuit unit, and the other end of which is connected to the collector of the first HBT tube HBTA in the multi-stage temperature coefficient unit.

[0013] Furthermore, the collector of the third HBT tube HBT3 is externally connected to a reference voltage, and the reference voltage is used to turn on the third HBT tube HBT3.

[0014] Furthermore, the standard current mirror bias unit also includes a second HBT tube HBT2, the other end of the resistor R2 is also connected to the base of the second HBT tube HBT2, the emitter output terminal of the second HBT tube HBT2 is connected to the base of the first HBT tube HBT1, and the collector of the second HBT tube HBT2 is externally connected to a reference voltage.

[0015] Furthermore, the output circuit unit further includes a capacitor C, and the other path of the reference current output by the temperature compensation unit is simultaneously connected to the ground through the capacitor C.

[0016] Furthermore, the emitter output end of the third HBT tube HBT3 is connected to a power amplifier unit, which includes a power amplifier, an input impedance matching unit connected to the input end of the power amplifier, and an output impedance matching unit connected to the output end of the power amplifier.

[0017] Furthermore, the input end of the input impedance matching unit and the output end of the output impedance matching unit are respectively connected to a DC blocking capacitor.

[0018] Furthermore, the input impedance matching unit and the output impedance matching unit are both LC impedance matching circuits.

[0019] Furthermore, the collector of the power amplifier is externally connected to a power supply Vd, and a choke inductor L0 is further connected between the collector of the power amplifier and the power supply Vd.

[0020] The beneficial effects of the present invention are:

[0021] (1) The bias circuit provided by the present invention sets a multi-order temperature coefficient voltage unit in a replica circuit unit of a standard current mirror bias unit, which simplifies the circuit and is conducive to on-chip integration.

[0022] (2) The present invention controls the operation of the second HBT tube HBT2 and the transistor on the output side of the current mirror through an external reference voltage. The collector of the transistor is not energized and is not turned on, thereby reducing power consumption during use.

[0023] (3) The present invention changes the basic current mirror structure and utilizes the current amplification function of the second HBT tube HBT2 to reduce the diversion of the base current of the replica side transistor to the reference current, thereby improving the transmission accuracy between the output bias current and the input reference current and outputting a stable bias current. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 A schematic diagram of the components of a power amplifier bias circuit based on a GaAs HBT process provided by an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of the circuit connection structure of a power amplifier bias circuit based on a GaAs HBT process provided by an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the circuit connection structure of a first-order temperature compensation bias circuit of a power amplifier bias circuit based on a GaAs HBT process provided by an embodiment of the present invention;

[0028] Figure 4 A schematic diagram of the circuit connection structure of a second-order temperature compensation bias circuit of a power amplifier bias circuit based on a GaAs HBT process provided by an embodiment of the present invention;

[0029] Figure 5 A schematic diagram of the circuit connection structure of a third-order temperature compensation bias circuit of a power amplifier bias circuit based on a GaAs HBT process provided by an embodiment of the present invention;

[0030] Figure 6 A schematic diagram of the circuit connection structure of an application circuit of a first-order temperature compensation bias circuit;

[0031] Figure 7 A schematic diagram of the circuit connection structure of an application circuit of a second-order temperature compensation bias circuit;

[0032] Figure 8 A schematic diagram of the circuit connection structure of an application circuit of a third-order temperature compensation bias circuit;

[0033] Figure 9 This is a temperature drift curve of the application circuit of the first-order temperature compensation bias circuit;

[0034] Figure 10 The temperature drift curve of the application circuit of the second-order temperature compensation bias circuit is shown in FIG.

[0035] Figure 11 The temperature drift curve of the application circuit of the third-order temperature compensation bias circuit is shown in FIG.

[0036] Figure 12 The figure below compares the temperature drift curves of the application circuits of first-order, second-order, and third-order temperature compensation bias circuits. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Example

[0039] like Figures 1 to 12As shown, the present invention provides a power amplifier bias circuit based on a GaAs HBT process, comprising a temperature compensation unit, a standard current mirror bias unit, and a multi-stage temperature coefficient voltage unit. The standard current mirror bias unit comprises a replica circuit unit and an output circuit unit. A first HBT tube HBT1 and a third HBT tube HBT3 are respectively disposed in the replica circuit unit and the output circuit unit. The multi-stage temperature coefficient voltage unit is disposed in the replica circuit unit and comprises a plurality of HBT tubes HBTA0 to HBTAi connected in series with collectors and bases connected, wherein the emitter output terminal of the last HBT tube HBTAi is connected to the collector of the first HBT tube HBT1, and the emitter of the first HBT tube HBT1 is grounded.

[0040] like Figure 1 and Figure 2 As shown, a power supply Vc is provided in the temperature compensation unit. The reference current outputted by the power supply Vc passes through the HBT tubes HBTA0 to HBTAi connected in series to the first HBT tube HBT1 and then to ground. The other path passes through the base of the third HBT tube HBT3 and then outputs the bias current Ibias from the emitter. In other words, the reference current outputted by the temperature compensation unit passes through the replica circuit including the multi-stage temperature coefficient voltage unit and the other path passes to the output circuit unit. Finally, the output circuit unit outputs the stable bias current Ibias.

[0041] Considering the impact of the self-heating effect of a GaAs HBT process-based power amplifier chip on the performance of a current source bias circuit connected to the power amplifier during operation, namely, the HBT self-heating effect deteriorates the image accuracy and temperature characteristics of this bias circuit. The present invention provides a small-sized bias circuit that can achieve multi-stage temperature compensation and improve transmission accuracy.

[0042] According to the temperature characteristics of the HBT tube, when the temperature inside the chip rises, the R be The base current increases, and thus the collector current increases, which in turn causes the output bias current temperature drift. The temperature compensation principle of the multi-order temperature coefficient voltage unit proposed in the present invention is as follows:

[0043] like Figure 2 As shown, the bases and collectors of several HBT tubes HBT0 to HBTAi in the multi-stage temperature coefficient voltage unit are short-circuited to form several diodes connected in series (i ≥ 0 and is an integer). When the temperature inside the chip rises, the temperature characteristics of the diodes reduce the voltage drop across the diodes, and the current in the series branch decreases, further compensating for the current increase caused by the thermoelectric positive feedback of the collector of the first HBT tube HBT1, so that the collector current of the first HBT tube HBT1 decreases.

[0044] As a further improvement of the present invention, the temperature compensation unit includes a diode and a resistor R1. The diode is connected between the power supply Vc and the resistor R1. One path of the current at the power supply end passes through the diode and the resistor R1 and is then grounded. Another path of the current passes through the diode and is connected to the input end of the standard current mirror bias unit, thereby providing a reference current for the standard current mirror bias unit.

[0045] Among them, the resistor R1 to ground is used for voltage division. By changing the value of the resistor R1, the reference current output by the temperature compensation unit can be adjusted. Furthermore, when the temperature compensation unit senses that the internal temperature of the chip has increased, it can be seen from the temperature characteristics of the above-mentioned diode that the voltage drop across the diode decreases, causing the reference current output by the temperature compensation unit to decrease accordingly.

[0046] To facilitate control of the bias current Ibias output by the standard current mirror bias unit, the replica circuit unit also includes a resistor R2. One end of resistor R2 serves as the current input for the replica circuit unit, and the other end is connected to the collector of the first HBT transistor HBTA0 in the multi-stage temperature coefficient unit. Resistor R2 is adjustable. As the resistance of resistor R2 increases, the bias voltage generated by the replica circuit unit at the bias point decreases, and the bias current Ibias output by the output circuit unit also decreases. This allows precise control of the output bias current Ibias by varying the resistance of resistor R2.

[0047] Furthermore, the collector of the third HBT transistor HBT3 is externally connected to a reference voltage Vref. The reference voltage Vref is used to turn on the third HBT transistor HBT3 and control its operating state. When the reference voltage Vref is greater than the turn-on voltage of the third HBT transistor HBT3 and the base current increases to a certain level, the third HBT transistor HBT3 turns on and operates in the saturation region, the output circuit unit operates, and outputs the bias current Ibias. When the reference voltage Vref is zero or less than the turn-on voltage of the third HBT transistor HBT3, the third HBT transistor HBT3 turns off. That is, regardless of the base current, the third HBT transistor HBT3 does not operate.

[0048] As a further limitation of the present invention, the standard current mirror bias unit further includes a second HBT transistor HBT2. The other end of resistor R2 is also connected to the base of the second HBT transistor HBT2. The emitter output terminal of the second HBT transistor HBT2 is connected to the base of the first HBT transistor HBT1. The collector of the second HBT transistor HBT2 is externally connected to a reference voltage Vref. Preferably, the second HBT transistor HBT2 has the same characteristics as the first HBT transistor HBT1. When the circuit is operating, the second HBT transistor HBT2 drives the first HBT transistor HBT1 to operate in a saturation region, so that the emitter output terminal of the first HBT transistor HBT1 outputs a stable amplified current.

[0049] Specifically, in a common current mirror structure, to ensure that the transistor on the replica side operates in the saturation region and outputs a stable mirror current, the base and collector of the replica side transistor are usually short-circuited so that its base current and collector current are equal, providing a static operating point of the base and thus a stable current-to-voltage value (Vgs). However, this current mirror circuit ignores the impact of the transistor base current on the bias current output of the entire current mirror. If the transistor amplification factor β is a small value, the bias current output in the current mirror and the input reference current will differ significantly.

[0050] Therefore, this embodiment utilizes the current amplification function of the second HBT tube HBT2 to reduce the shunting of the reference current by the base current of the first HBT tube HBT1, thereby improving the transmission accuracy between the output bias current and the input reference current and outputting a stable bias current Ibias.

[0051] In order to make the output circuit unit output a stable bias current, the output circuit unit further includes a grounding capacitor C. The other path of the reference current output by the temperature compensation unit is simultaneously grounded through the capacitor C.

[0052] As a preferred embodiment of the present invention, the emitter output terminal of the third HBT tube HBT3 is connected to a power amplifier unit, which includes a power amplifier, an input impedance matching unit connected to the input terminal of the power amplifier, and an output impedance matching unit connected to the output terminal of the power amplifier. The input impedance matching unit and the output impedance matching unit are used to ensure effective reception and transmission of the power amplifier unit. Both are LC impedance matching circuits, wherein the input impedance matching unit includes an inductor L1 and a capacitor C2, and the output impedance matching unit includes an inductor L2 and a capacitor C3.

[0053] The power amplifier unit also includes a DC blocking capacitor C1 and a DC blocking capacitor C4. The RF power signal is input from the RF signal input terminal RFin, connected to the base of the power amplifier HBT_PA through the DC blocking capacitor C1 and the input impedance matching unit, and the amplified signal output from the collector of the power amplifier HBT_PA is output from the RF signal output terminal RFout after passing through the output impedance matching unit and the DC blocking capacitor C4.

[0054] The emitter of the power amplifier HBT_PA is grounded, and the collector is connected to an external voltage Vd through a choke inductor L0. The inductor L0 reduces the instantaneous current impact on the collector of the power amplifier HBT_PA after power is applied, and is used to suppress high-frequency noise of the power line and stabilize the current.

[0055] Based on the design of the multi-stage temperature coefficient voltage unit, the present invention also provides three embodiments, such as Figure 3 、 Figure 4 and Figure 5 The following diagrams show a first-order temperature compensation bias circuit, a second-order temperature compensation bias circuit, and a third-order temperature compensation bias circuit. Furthermore, in temperature drift simulation testing, the component values and transistor characteristics within each of the multiple-order temperature compensation bias circuits must remain consistent. Specifically, the power supply Vc = 5V, the reference voltage Vref = 2V, R1 = 2kΩ, R2 is adjustable from 1.6kΩ to 2.4kΩ, and C is adjustable from 0.3pF to 1pF.

[0056] Example 1:

[0057] like Figure 3 As shown, the first-order temperature compensation bias circuit does not include a multi-order temperature coefficient voltage unit. The entire bias circuit relies solely on the temperature compensation unit and the thermoelectric negative feedback characteristics of the collector current unique to the HBT tube to perform temperature compensation. The base and emitter of the second HBT tube HBT2 are connected to the collector and base of the first HBT tube HBT1, respectively. The current flowing through the resistor R2 enters the base of the second HBT tube HBT2 in one path and the collector of the first HBT tube HBT1 in the other path.

[0058] Furthermore, the application circuit of the first-order temperature compensation bias circuit ( Figure 6 ) simulation test Figure 9 As shown, when in the bias circuit, the power supply Vc = 5V, the reference voltage Vref = 2V, R1 = 2KΩ, R2 = 2.1KΩ, and C = 0.7pF, after the internal temperature of the control chip changes, the output bias current range fluctuates greatly.

[0059] Example 2:

[0060] like Figure 4 As shown, the second-order temperature compensation bias circuit includes a multi-order temperature coefficient voltage unit, in which an HBT tube HBTA0 with a collector and a base connected is provided. The temperature characteristics of the diode are used to perform temperature compensation on the bias circuit.

[0061] Furthermore, the application circuit of the second-order temperature compensation bias circuit ( Figure 7 ) simulation test Figure 10 As shown, when in the bias circuit, power supply Vc = 5V, reference voltage Vref = 2V, R1 = 2KΩ, R2 = 2.1KΩ, C = 0.7pF, after the internal temperature of the control chip changes, the output bias current fluctuation range becomes smaller than that of the first-order temperature compensation bias circuit.

[0062] Example 3:

[0063] like Figure 5As shown, the third-order temperature compensation bias circuit includes a multi-order temperature coefficient voltage unit, in which HBT tubes HBTA0 and HBTA1 are connected in series with the collector and base connected. The temperature characteristics of the two diodes are used to perform temperature compensation on the bias circuit.

[0064] Furthermore, the application circuit of the third-order temperature compensation bias circuit ( Figure 8 ) simulation test Figure 11 As shown, when in the bias circuit, the power supply Vc = 5V, the reference voltage Vref = 2V, R1 = 2KΩ, R2 = 2.1KΩ, C = 0.7pF, after the internal temperature of the control chip changes, the output bias current range fluctuation further becomes smaller.

[0065] The three embodiments above change the internal temperature of the chip under different orders of temperature compensation, and the temperature drift curves obtained by simulation are compared. Figure 12 As shown in FIG, as the order increases, the fluctuation range of the bias current output by the bias circuit becomes smaller and smaller.

[0066] This invention provides a power amplifier bias circuit based on a GaAs HBT process. This circuit can be designed with different stages to control the temperature drift range based on chip area requirements, current drift requirements, and temperature variations. This design offers the advantages of simplicity, efficiency, and miniaturization. Simulation results show that multiple stages improve the current temperature drift curve and significantly reduce the temperature variation range. A comprehensive design should consider both the layout area and the actual temperature drift.

[0067] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A power amplifier bias circuit based on GaAs HBT technology, characterized in that: The device comprises a temperature compensation unit, a standard current mirror bias unit, and a multi-stage temperature coefficient voltage unit. The standard current mirror bias unit comprises a replica circuit unit and an output circuit unit. A first HBT tube HBT1 and a third HBT tube HBT3 are respectively provided in the replica circuit unit and the output circuit unit. The multi-stage temperature coefficient voltage unit is provided in the replica circuit unit and comprises a plurality of HBT tubes HBTA connected in series with collectors and bases connected, wherein the emitter output terminal of the last HBT tube HBTA is connected to the collector of the first HBT tube HBT1, and the emitter of the first HBT tube HBT1 is grounded. The temperature compensation unit is provided with a power supply Vc, which outputs a reference current which passes through the HBT tubes HBTA connected in series to the first HBT tube HBT1 and then to ground, and another which passes through the third HBT tube HBT3 and then outputs a bias current; The replica circuit unit further includes a resistor R2, one end of which serves as the current input of the replica circuit unit, and the other end of which is connected to the collector of the first HBT tube HBTA in the multi-order temperature coefficient unit; The standard current mirror bias unit also includes a second HBT transistor HBT2. The other end of the resistor R2 is also connected to the base of the second HBT transistor HBT2. The emitter output terminal of the second HBT transistor HBT2 is connected to the base of the first HBT transistor HBT1. The collector of the second HBT transistor HBT2 is externally connected to a reference voltage.

2. The power amplifier bias circuit based on GaAs HBT process according to claim 1, characterized in that: The temperature compensation unit includes a diode and a resistor R1. The diode is connected between the power supply and the resistor. One path of the current at the power supply end passes through the diode and the resistor and is then grounded. The other path of the current passes through the diode and is connected to the standard current mirror bias unit, so as to provide a reference current for the standard current mirror bias unit.

3. The power amplifier bias circuit based on GaAs HBT process according to claim 1, characterized in that: The collector of the third HBT tube HBT3 is externally connected to a reference voltage, and the reference voltage is used to turn on the third HBT tube HBT3.

4. The power amplifier bias circuit based on GaAs HBT process according to claim 1, characterized in that: The output circuit unit further includes a capacitor C, and the other path of the reference current output by the temperature compensation unit is grounded through the capacitor C at the same time.

5. The power amplifier bias circuit based on GaAs HBT process according to claim 1, characterized in that: The emitter output end of the third HBT tube HBT3 is connected to a power amplifier unit, which includes a power amplifier, an input impedance matching unit connected to the input end of the power amplifier, and an output impedance matching unit connected to the output end of the power amplifier.

6. The power amplifier bias circuit based on GaAs HBT process according to claim 5, characterized in that: The input end of the input impedance matching unit and the output end of the output impedance matching unit are respectively connected to a DC blocking capacitor.

7. The power amplifier bias circuit based on GaAs HBT process according to claim 5, characterized in that: The input impedance matching unit and the output impedance matching unit are both LC impedance matching circuits.

8. The power amplifier bias circuit based on GaAs HBT process according to claim 5, characterized in that: The collector of the power amplifier is externally connected to a power supply Vd, and a choke inductor L0 is further connected between the collector of the power amplifier and the power supply Vd.

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