There are usually many resistors in the circuit design. When the circuit design buffer, a resistor is usually added to the operational amplifier feedback path. Many junior engineers don't understand why a resistor is added here, but the design makes sense. In fact, the design of the resistor is very meaningful, which can stably improve the stability of the circuit, as shown below:
In this circuit we can see a resistor. The resistors for this circuit are typically used in low-speed applications <50 MHz to eliminate the DC offset problem caused by the op amp input bias current. The R2 resistor may also provide some protection for the inverting input when there is an electrostatic discharge (ESD) shock on the output. In addition, some op amps produce lower distortion if the two inputs have matching supply impedances. However, if you do not understand the purpose of the R2 resistor, this value is usually chosen at random, resulting in instability.
   
In understanding the cause of the instability caused by the R2 resistor, we add the input capacitance of the operational amplifier to the circuit. This design can solve the problem of the circuit well. The value of the correct R2 resistor can effectively improve the stability of the circuit. If the engineer does not correctly understand the R2 resistor when designing, the design circuit will inevitably cause instability.