Protection circuit and output circuit of operational amplifier

Abstract

The invention discloses a protection circuit of an operational amplifier. The protection circuit resists electrostatic discharge. The protection circuit comprises N transmission gate resistance circuits which are connected in parallel, N is a positive integer larger than 1, the input end of each transmission gate resistance circuit is connected to the output end of the operational amplifier, the output end of each transmission gate resistance circuit is connected to the output end of the protection circuit, and the output end of each transmission gate resistance circuit is connected to the output end of the operational amplifier. Each transmission gate resistance circuit sequentially comprises a transmission gate circuit and a resistor which are connected in series, the transmission gate circuit of each transmission gate resistance circuit receives on-off control of a first voltage control signal and a second voltage control signal, and the first voltage control signal and the second voltage control signal are opposite in phase.

Description

Technical Field

[0001] This application belongs to the field of electrostatic discharge (ESD, Electro-Static Discharge) protection, and relates to an electrostatic discharge protection circuit composed of a controllable switch circuit. Background Art

[0002] Operational amplifiers are common components in modern electronic circuits and are usually used to output signals to external circuits. Operational amplifiers are typically composed of multiple transistors. When the external circuit encounters electrostatic discharge, external charges will invade the operational amplifier, causing damage to the N-type or P-type transistors inside the operational amplifier.

[0003] To avoid damage to the operational amplifier caused by electrostatic discharge, an output resistor can be added after the output terminal of the operational amplifier to protect the transistors inside the operational amplifier from charge damage. However, when the resistance value of the output resistor is too small, it is unable to block too large static charges. On the contrary, when the resistance value of the output resistor is too large, it will greatly affect the signal at the output terminal of the operational amplifier.

[0004] Therefore, there is an urgent need for a circuit design that can both protect the operational amplifier from relatively large electrostatic discharge damage and not significantly affect the signal at the output terminal of the operational amplifier. Summary of the Invention

[0005] This application is a protection circuit for an operational amplifier proposed to solve the deficiencies in the prior art, aiming to provide a transmission gate circuit at the output terminal of the operational amplifier and the protection against electrostatic discharge of the operational amplifier.

[0006] To achieve the above objective, this application adopts the following technical solutions:

[0007] A protection circuit for an operational amplifier, characterized in that it includes N transmission gate resistor circuits connected in parallel, where N is a positive integer greater than 1. The input terminal of each of the transmission gate resistor circuits is connected to the output terminal of the operational amplifier, the output terminal of each of the transmission gate resistor circuits is connected to the output terminal of the protection circuit, each of the transmission gate resistor circuits sequentially includes a series-connected transmission gate circuit and a resistor, and the transmission gate circuit of each of the transmission gate resistor circuits is controlled by a first voltage control signal and a second voltage control signal for switching, and the first voltage control signal and the second voltage control signal are in anti-phase with each other.

[0008] Preferably, in order to allow the charges of electrostatic discharge to pass through the N transmission gate resistor circuits evenly to improve the protection against electrostatic discharge of each transmission gate resistor circuit, it is characterized in that the resistance values of the resistors of each of the transmission gate resistor circuits are the same.

[0009] Preferably, in order to further protect the transmission gate circuit at the output end of the operational amplifier and the operational amplifier, it is characterized in that it further includes a first diode, the positive electrode of the first diode is connected to the output ends of the N transmission gate resistor circuits, and the negative electrode of the first positive electrode body is connected to the power supply.

[0010] Preferably, in order to further protect the transmission gate circuit at the output end of the operational amplifier and the operational amplifier, it is characterized in that it further includes a second diode, the negative electrode of the second diode is connected to the output ends of the N transmission gate resistor circuits, and the positive electrode of the second positive electrode body is connected to the ground potential.

[0011] Preferably, in order to make the transmission gate circuit applicable to the same manufacturing process of other components, it is characterized in that each transmission gate circuit of the transmission gate resistor circuit includes a P-type transistor and an N-type transistor made of complementary metal oxide semiconductor.

[0012] According to an embodiment of the present application, an output circuit of an operational amplifier is provided, which is characterized in that it includes the operational amplifier and the protection circuit of the operational amplifier as described above.

[0013] Due to the above-mentioned solution, the beneficial effects of the present application are as follows: it provides better electrostatic discharge protection ability, and can prevent the operational amplifier and the semiconductor components of the transmission gate at the output end of the operational amplifier from being damaged by large electrostatic discharges, and will not greatly affect the signal at the output end of the operational amplifier. Description of the Drawings

[0014] Figure 1 It is a schematic diagram of the output circuit 100 of the operational amplifier according to the embodiment of the present application.

[0015] Figure 2 It is a schematic diagram of a transmission gate circuit 120 according to an embodiment of the present application.

[0016] Figure 3 It is a schematic diagram of the output circuit 300 of the operational amplifier according to the embodiment of the present application.

[0017] Figure 4 It is a schematic diagram of the protection circuit module 320 according to the embodiment of the present application.

[0018] Figure 5 It is a schematic diagram of the transmission gate resistor circuit 400 according to the embodiment of the present application. Detailed Embodiments

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope protected by the present application.

[0020] The terms "first", "second", "third", etc. (if any) in the description, claims, and drawings of the present application are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that these described objects can be interchanged under appropriate circumstances. In the description of the present application, the meaning of "a plurality" is two or more, unless otherwise specifically defined. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware circuits or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0021] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

[0022] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a connection that can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0023] To make the purpose, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the drawings and specific implementation manners.

[0024] Please refer to Figure 1As shown, it is a schematic diagram of the output circuit 100 of an operational amplifier according to an embodiment of the present application. The above-mentioned output circuit 100 of the operational amplifier includes an operational amplifier 110 and an operational amplifier protection circuit. The operational amplifier protection circuit includes a transmission gate circuit 120, a resistor 130, and an output port 140. Between the resistor 130 and the output terminal, a power supply and a ground potential are also respectively connected. The input terminal of the transmission gate circuit 120 is connected to the output terminal of the operational amplifier 110.

[0025] When the electrostatic discharge charge transmitted by the external circuit enters the operational amplifier protection circuit from the output port 140, it will first pass through the current limiting of the resistor 130. Then, it will pass through the voltage reduction of the transmission gate circuit 120. The output gate circuit 120 and the resistor 130 play a role in protecting the operational amplifier.

[0026] Please refer to Figure 2 As shown, it is a schematic diagram of a transmission gate circuit 120 according to an embodiment of the present application. The transmission gate circuit 120 may include a P-type transistor 210 and an N-type transistor 220. The drain of the P-type transistor 210 is connected to the source of the N-type transistor 220. Similarly, the source of the P-type transistor 210 is connected to the drain of the N-type transistor 220. The input terminal of the transmission gate circuit 120 is on the left side, and the output terminal is on the right side.

[0027] The gate of the P-type transistor 210 is connected to the first voltage control signal V control . The gate of the N-type transistor 220 is connected to the second voltage control signal where the first voltage control signal V control and the second voltage control signal are inverse signals. When the first voltage control signal V control represents the logic signal 1, and its inverted second voltage control signal represents the logic signal 0, the transmission gate circuit 120 will conduct. The output terminal will be equal to the input terminal. Conversely, when the first voltage control signal V control represents the logic signal 0, and its inverted second voltage control signal represents the logic signal 1, the transmission gate circuit 120 will be closed and will not output the signal of the input terminal.

[0028] The transmission gate circuit 120 can be a component made of complementary metal oxide semiconductor (CMOS, Complementary Metal Oxide Semiconductor). The above-mentioned P-type transistor 210 and N-type transistor 220 can be metal oxide semiconductor field effect transistors (MOSFET, Metal-Oxide Semiconductor Field Effect Transistor).

[0029] Those of ordinary skill in the art should understand that in other embodiments, the transmission gate circuit 120 can also be implemented using a pair of bipolar transistors with opposite polarities. The present application does not limit the implementation manner of the transmission gate circuit 120. As a controllable switch circuit, the transmission gate circuit 120 has a very low on-resistance and a very high off-resistance. For example, the above-mentioned on-resistance may be on the order of several hundred ohms, and the above-mentioned off-resistance may be on the order of billions of ohms.

[0030] Please refer to Figure 3 shown, which is a schematic diagram of the output circuit 300 of the operational amplifier according to an embodiment of the present application. And Figure 1 compared with the operational amplifier protection circuit shown, Figure 3 the protection circuit of the operational amplifier shown uses a protection circuit module 320 to replace the series-connected transmission gate circuit 120 and resistor 130. In addition, at the output end of the protection circuit module 320, the power supply can be connected by connecting the positive electrode of the first diode 331, and the ground potential can be connected by connecting the negative electrode of the second diode 332.

[0031] Please refer to Figure 4 shown, which is a schematic diagram of the protection circuit module 320 according to an embodiment of the present application. The protection circuit module 320 includes a plurality of parallel-connected transmission gate resistor circuits 400-1, transmission gate resistor circuits 400-2,..., up to transmission gate resistor circuits 400-N. In Figure 4 the embodiment shown, it includes N transmission gate resistor circuits 400, where N is a positive integer greater than 1.

[0032] The input end of each transmission gate resistor circuit 400 is connected to the output end of the operational amplifier 110. The output end of each transmission gate resistor circuit 400 is connected to the output end of the operational amplifier protection circuit, the positive electrode of the first diode 331, and the negative electrode of the second diode 332. Each transmission gate resistor circuit 400 receives the aforementioned first voltage control signal V control and its inverted second voltage control signal for control.

[0033] Please refer to Figure 5 shown, which is a schematic diagram of the transmission gate resistor circuit 400 according to an embodiment of the present application. The transmission gate resistor circuit 400 includes a series-connected transmission gate circuit 520 and resistor 530. The transmission gate circuit 520 here can also be applied to the previously described embodiments and Figure 2 the embodiment shown, that is, it receives the aforementioned first voltage control signal V control and its inverted second voltage control signal Control. The function of each transmission gate resistor circuit 400 has been described as in Figure 1 the embodiment of, and can be used to prevent electrostatic discharge damage to the operational amplifier 110.

[0034] In one embodiment, the resistance values of each resistor 530 can be the same. The charge of the electrostatic discharge will be evenly distributed to the N parallel transmission gate circuits 520. In other words, the probability of electrostatic discharge damage suffered by a pair of transistors included in each transmission gate circuit 520 is reduced.

[0035] In one embodiment, the resistance value of the resistor 530 can be Figure 1 N times the resistance value R of the resistor 130 of, and its resistance value is NxR. From the output terminal of the operational amplifier 110, the protection circuit module 320 is connected in parallel with N transmission gate resistor circuits 400, and its equivalent output resistance is the same as that of Figure 1 the single resistor 130 with a resistance value R in the embodiment. In this way, the output signal of the operational amplifier 110 will not be affected. That is to say Figure 1 and Figure 3 the output signal of the operational amplifier protection circuit shown can be the same.

[0036] In addition, when the resistance value of the resistor 530 is greater than the resistance value R of the resistor 130, the possibility of electrostatic discharge damage suffered by the transmission gate circuit 520 is reduced compared to the transmission gate circuit 120. That is to say, due to the N transmission gate resistor circuits 400 sharing the charge of the electrostatic discharge and the increase in the resistance value of the resistor 530, the protection ability of the transmission gate circuit 520 against electrostatic discharge is increased compared to the transmission gate circuit 120.

[0037] Since the protection ability of the entire protection circuit 320 against electrostatic discharge is increased, it can naturally protect the transmission gate circuit at the output terminal of the operational amplifier 110 and the operational amplifier 110.

[0038] According to an embodiment of the present application, a protection circuit for an operational amplifier is provided, characterized in that it includes N transmission gate resistor circuits connected in parallel, where N is a positive integer greater than 1, and the input terminal of each of the transmission gate resistor circuits is connected to the output terminal of the operational amplifier, the output terminal of each of the transmission gate resistor circuits is connected to the output terminal of the protection circuit, each of the transmission gate resistor circuits sequentially includes a series-connected transmission gate circuit and a resistor, and the transmission gate circuit of each of the transmission gate resistor circuits is controlled by a first voltage control signal and a second voltage control signal for switching, and the first voltage control signal and the second voltage control signal are in opposite phases.

[0039] Preferably, in order to evenly distribute the charge of the electrostatic discharge across the N transmission gate resistor circuits, thereby enhancing the protection of each transmission gate resistor circuit against electrostatic discharge, each of the resistors in the transmission gate resistor circuits has the same resistance value.

[0040] Preferably, to further protect the transmission gate circuit at the output of the operational amplifier and the operational amplifier, it is characterized by further comprising a first diode, the anode of the first diode being connected to the output terminals of the N transmission gate resistor circuits, and the cathode of the first diode being connected to the power supply.

[0041] Preferably, to further protect the transmission gate circuit at the output of the operational amplifier and the operational amplifier, it is characterized by further comprising a second diode, the cathode of the second diode being connected to the output terminals of the N transmission gate resistor circuits, and the anode of the second diode being connected to the ground potential.

[0042] Preferably, to enable the transmission gate circuit to be applicable to the same manufacturing process of other components, each of the transmission gate resistor circuits includes a P-type transistor and an N-type transistor made of complementary metal-oxide-semiconductor.

[0043] According to an embodiment of the present application, there is provided an output circuit of an operational amplifier, which is characterized by including the aforementioned operational amplifier and the protection circuit of the operational amplifier.

[0044] The protection circuit and the output circuit of the operational amplifier provided by the present application offer better protection against electrostatic discharge, can prevent the operational amplifier and the semiconductor components of the transmission gate at the output of the operational amplifier from being damaged by large electrostatic discharges, and will not significantly affect the signal at the output of the operational amplifier.

[0045] As described above, the above are only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application, based on the technical solution and the inventive concept of the present application, makes equivalent substitutions or modifications, and all should be covered by the protection scope of the present application.

Claims

1. A protection circuit for an operational amplifier, characterized in that: Include: N transmission gate resistor circuits connected in parallel, where N is a positive integer greater than 1, The input end of each transmission gate resistance circuit is connected to the output end of the operational amplifier, the output end of each transmission gate resistance circuit is connected to the output end of the protection circuit, each transmission gate resistance circuit includes a transmission gate circuit and a resistor connected in series in sequence, and the transmission gate circuit of each transmission gate resistance circuit accepts switch control of a first voltage control signal and a second voltage control signal, and the first voltage control signal and the second voltage control signal are inverted to each other.

2. The operational amplifier protection circuit according to claim 1, wherein: The resistance value of each resistor in the transmission gate resistance circuit is the same.

3. The protection circuit of the operational amplifier according to claim 1, wherein: It further comprises: a first diode, wherein the anode of the first diode is connected to the output ends of the N transmission gate resistance circuits, and the cathode of the first anode is connected to a power supply.

4. The operational amplifier protection circuit according to claim 1, wherein: It further comprises: a second diode, wherein the cathode of the second diode is connected to the output ends of the N transmission gate resistance circuits, and the anode of the second anode body is connected to the ground potential.

5. The operational amplifier protection circuit according to claim 1, wherein: Each transmission gate circuit of the transmission gate resistor circuit includes a P-type transistor and an N-type transistor made of complementary metal oxide semiconductor.

6. An output circuit of an operational amplifier, characterized in that: An operational amplifier as claimed in any one of claims 1 to 5 and a protection circuit for the operational amplifier.

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