Operational amplifier input protection circuit

Abstract

The utility model relates to an input protection circuit of an operational amplifier. The input protection circuit comprises an overvoltage protection circuit, an electrostatic protection circuit, an operational amplifier I and an operational amplifier II, the electrostatic protection circuit comprises a resistor R1 and a capacitor C; the input end of the overvoltage protection circuit is connected with a voltage input end IN, the overvoltage protection circuit is connected with the input end of the operational amplifier I through a resistor R1, the output end of the operational amplifier I is connected with the operational amplifier II, and the output end of the operational amplifier II is connected between the resistor R1 and the input end of the operational amplifier I through a capacitor C. And the electrostatic protection circuit is electrically connected with the overvoltage protection circuit, so that the stability and normal distribution of current can be ensured. According to the operational amplifier, flexibility and convenience are considered in the circuit design process, various use requirements are met, the excellent protection effect and stability are achieved, the use efficiency of the operational amplifier is greatly improved, and the service life of the operational amplifier is greatly prolonged.

Description

Technical Field

[0001] The utility model belongs to the field of electronic information, and more specifically relates to an operational amplifier input protection circuit. Background Art

[0002] Operational amplifiers (OPA) are key components used in a wide range of electronic devices. They amplify electrical signals to perform various signal processing tasks, such as filtering, amplification, analog integration, differentiation, and addition. Due to their high input impedance, low output impedance, wide bandwidth, and highly flexible gain adjustment, operational amplifiers play a crucial role in analog electronic circuits.

[0003] While operational amplifiers (OPA) offer numerous advantages as analog signal processing components, they are not without disadvantages. For example, exposure of the OPA input to excessive voltage or electrostatic shock can damage the semiconductor components within the OPA, necessitating appropriate protection.

[0004] Detecting weak signals is a common requirement in fields such as communications, instrumentation, and biomedicine. These signals, in the form of voltage, current, or optoelectronics, typically require an amplifier for amplification before subsequent signal analysis and processing. Because these signals are so weak, the amplifier must possess low noise, high input impedance, high common-mode rejection ratio, and low power consumption to ensure the amplified signal is not overwhelmed by noise or interference. Summary of the Invention

[0005] The utility model effectively protects the sensitive parts of the operational amplifier to the input, avoiding damage to the internal components of the operational amplifier caused by excessively high input voltage or electrostatic shock. At the same time, it also needs to meet the requirements of simple structure and rapid response. It can quickly respond and provide protection when the input voltage is momentarily too high or there is electrostatic shock, so as to improve the reliability and stability of the operational amplifier and the entire circuit system.

[0006] In order to achieve the above object, the utility model is implemented by adopting the following technical solutions: the input protection circuit includes an overvoltage protection circuit, an electrostatic protection circuit, an operational amplifier I, and an operational amplifier II; the overvoltage protection circuit, the electrostatic protection circuit, the operational amplifier I, and the operational amplifier II are electrically connected; the electrostatic protection circuit includes a resistor R1 and a capacitor C;

[0007] The input end of the overvoltage protection circuit is connected to the voltage input end IN, the overvoltage protection circuit is connected to the input end of the operational amplifier I through the resistor R1, the output end of the operational amplifier I is connected to the operational amplifier II, and the output end of the operational amplifier II is connected between the resistor R1 and the input end of the operational amplifier I through the capacitor C.

[0008] In one embodiment, the overvoltage protection circuit includes: a current limiting resistor Rin, a clamping diode D1, and a clamping diode D2; the electrostatic protection circuit includes a resistor R1 and a capacitor C;

[0009] One end of the current limiting resistor Rin is electrically connected to the voltage input terminal IN, and the other end of the current limiting resistor Rin is electrically connected to one end of the resistor R1 and the anode of the clamping diode D1;

[0010] The anode of the clamping diode D1 is electrically connected to the cathode of the clamping diode D2, the cathode of the clamping diode D1 is electrically connected to the power supply VCC terminal, and the clamping diode D2 is electrically connected to the power supply VSS terminal;

[0011] The other end of the resistor R1 is electrically connected to the positive input port of the operational amplifier I, and the output port of the operational amplifier I is electrically connected to the negative input port of the operational amplifier II;

[0012] The output end of the operational amplifier II is connected to the positive input port of the operational amplifier I through a capacitor C.

[0013] In one embodiment, the input protection circuit further includes an adjustable resistor R2, and the output port of the operational amplifier I is electrically connected to the negative input port of the operational amplifier II via the adjustable resistor R2.

[0014] In one embodiment, the input protection circuit further includes a clamping diode D3 and a clamping diode D4; the output end of the operational amplifier II is electrically connected to the cathode of the clamping diode D3 and the anode of the clamping diode D4 via a capacitor C; the anode of the clamping diode D3 is electrically connected to the cathode of the clamping diode D4 and then connected to the positive input port of the operational amplifier I.

[0015] Beneficial effects of the utility model:

[0016] The beneficial effects of this utility model lie in the design of an operational amplifier input protection circuit that includes an overvoltage protection circuit and an electrostatic protection circuit. The overvoltage protection circuit effectively limits the input voltage, preventing damage to the operational amplifier's internal components caused by excessive voltage, while the electrostatic protection circuit effectively suppresses the effects of static electricity on the operational amplifier, preventing damage to the amplifier. This comprehensive protection design enhances the reliability and safety of the operational amplifier and the entire circuit system, improving its operational stability. The overall structure is simple and easy to implement, significantly extending the service life and safety of electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A circuit diagram provided as an example of the present invention;

[0018] Figure 2 This is a circuit diagram provided for another example of the present invention. DETAILED DESCRIPTION

[0019] The following describes embodiments of the present application in more detail with reference to the accompanying drawings. Although the accompanying drawings illustrate embodiments of the present application, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0020] In one example, if Figure 1 As shown, the input protection circuit includes an overvoltage protection circuit, an electrostatic protection circuit, an operational amplifier I, and an operational amplifier II. The overvoltage protection circuit, the electrostatic protection circuit, the operational amplifier I, and the operational amplifier II are electrically connected; the electrostatic protection circuit includes a resistor R1 and a capacitor C;

[0021] The input end of the overvoltage protection circuit is connected to the voltage input end IN, the overvoltage protection circuit is connected to the input end of the operational amplifier I through the resistor R1, the output end of the operational amplifier I is connected to the operational amplifier II, and the output end of the operational amplifier II is connected between the resistor R1 and the input end of the operational amplifier I through the capacitor C.

[0022] In another example, the overvoltage protection circuit includes: a current limiting resistor Rin, a clamping diode D1, and a clamping diode D2;

[0023] One end of the current limiting resistor Rin is electrically connected to the voltage input terminal IN, and the other end of the current limiting resistor Rin is electrically connected to one end of the resistor R1 and the anode of the clamping diode D1;

[0024] The anode of the clamping diode D1 is electrically connected to the cathode of the clamping diode D2, the cathode of the clamping diode D1 is electrically connected to the power supply VCC terminal, and the clamping diode D2 is electrically connected to the power supply VSS terminal;

[0025] The other end of the resistor R1 is electrically connected to the positive input port of the operational amplifier I. Preferably, the input protection circuit further includes an adjustable resistor R2, and the output port of the operational amplifier I is electrically connected to the negative input port of the operational amplifier II via the adjustable resistor R2.

[0026] Preferably, if Figure 2 As shown, the input protection circuit further includes a clamping diode D3 and a clamping diode D4; the output end of the operational amplifier II is electrically connected to the cathode of the clamping diode D3 and the anode of the clamping diode D4 through the capacitor C, and the anode of the clamping diode D3 is electrically connected to the cathode of the clamping diode D4 and then connected to the positive input port of the operational amplifier I.

[0027] Both operational amplifier I and operational amplifier II operate in negative feedback mode. The negative input terminal of operational amplifier I is directly electrically connected to the output terminal, and the negative input terminal of operational amplifier II is electrically connected to the output terminal through resistor R3.

[0028] Current-limiting resistor Rin limits the current, protecting subsequent circuits from damage caused by excessive current. Clamping diodes D1 and D2 clamp the voltage to prevent excessive input voltage, providing overvoltage protection. Clamping diodes D3 and D4 are included in the circuit to ensure that the preamplifier's input impedance is not affected by the electrostatic protection circuit.

[0029] Resistor R1 and capacitor C form a high-pass filter circuit to remove DC components from the input signal. Capacitor C is connected to the output of operational amplifier II to block DC and pass AC signals. Adjustable resistor R2 adjusts the negative feedback of the operational amplifier, changing its amplification factor.

[0030] The selected parameters are: Rin = 5KΩ, R1 = 100KΩ, R2 = 1KΩ adjustable resistor, C = 0.001uF. During the test, the simulated electrostatic signal applied to the input terminal IN has an amplitude of 4000V, a rise time of 10ns, and a duration of 200ns.

[0031] Operational amplifier I is used to amplify the input signal, while operational amplifier II is used to further amplify the signal, forming a two-stage amplifier circuit. Operational amplifier II, through negative feedback connection with operational amplifier I, can stabilize the amplification factor and improve linearity.

[0032] Working principle of this utility model: In the overvoltage protection circuit, if the input voltage is too high, the overvoltage may be transmitted to the inside of the circuit through the current limiting resistor Rin. When the voltage reaches a certain level, the clamping diodes D1 and D2 begin to conduct, and the voltage will be clamped at a certain value to prevent the overvoltage from damaging the input voltage.

[0033] The electrostatic protection circuit is used to prevent static interference. When the current passes through the current limiting resistor Rin, the resistor R1 and the capacitor C start working, and the static electricity is grounded, thereby preventing static electricity from damaging the operational amplifier.

[0034] Operational amplifier I and operational amplifier II are the core signal amplification links. Through the electrical connection between the two, the signal connected to the positive input port of operational amplifier I can be amplified. The amplified signal passes through capacitor C and the negative input port of operational amplifier II, and is amplified again by operational amplifier II to output a larger signal.

[0035] Adjustable resistor R2 adjusts the amplification factor. The signal input to the negative input port of operational amplifier II can be adjusted to change its amplification factor to better meet the application requirements. Clamping diodes D3 and D4 are connected to the circuit to ensure that the input impedance of the preamplifier is not affected by the electrostatic protection circuit.

[0036] The embodiments of the present application have been described above. The above description is illustrative and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to the technology in the market, or to enable other persons skilled in the art to understand the embodiments disclosed herein.

Claims

1. An operational amplifier input protection circuit, characterized in that: The operational amplifier input protection circuit includes: an overvoltage protection circuit, an electrostatic protection circuit, an operational amplifier I, and an operational amplifier II; the overvoltage protection circuit, the electrostatic protection circuit, the operational amplifier I, and the operational amplifier II are electrically connected; the electrostatic protection circuit includes a resistor R1 and a capacitor C; The input end of the overvoltage protection circuit is connected to the voltage input end IN, the overvoltage protection circuit is connected to the input end of the operational amplifier I via the resistor R1, the output end of the operational amplifier I is connected to the operational amplifier II, and the output end of the operational amplifier II is connected between the resistor R1 and the input end of the operational amplifier I via the capacitor C.

2. The operational amplifier input protection circuit according to claim 1, characterized in that: The overvoltage protection circuit comprises: a clamping diode D1, a clamping diode D2 and a current limiting resistor Rin; The anode of the clamping diode D1 is electrically connected to the cathode of the clamping diode D2, the cathode of the clamping diode D1 is electrically connected to the power supply VCC terminal, and the clamping diode D2 is electrically connected to the power supply VSS terminal; One end of the current limiting resistor Rin is electrically connected to the voltage input terminal IN, and the other end of the current limiting resistor Rin is connected between the anode of the clamping diode D1 and the cathode of the clamping diode D2, and the anode of the clamping diode D1 and the cathode of the clamping diode D2 are also connected to one end of the resistor R1; the other end of the resistor R1 is electrically connected to the same-direction input terminal of the operational amplifier I, and the reverse input terminal of the operational amplifier I is connected to the output terminal of the operational amplifier I; the output terminal of the operational amplifier I is electrically connected to the reverse input port of the operational amplifier II; The output end of the operational amplifier II is connected to the same-direction input end of the operational amplifier I through a capacitor C.

3. The operational amplifier input protection circuit according to claim 1, wherein: An adjustable resistor R2 is provided between the output end of the operational amplifier I and the reverse input end of the operational amplifier II.

4. The operational amplifier input protection circuit according to claim 1, wherein: The input protection circuit also includes a clamping diode D3 and a clamping diode D4; the output end of the operational amplifier II is electrically connected to the cathode of the clamping diode D3 and the anode of the clamping diode D4 through a capacitor C, and the anode of the clamping diode D3 is electrically connected to the cathode of the clamping diode D4 and then connected to the positive input port of the operational amplifier I.

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