In op-amp (operational amplifier) circuits, negative feedback is a fundamental concept used to stabilize and control the amplifier's performance. Negative feedback is a technique where a portion of the output signal is fed back to the input with a phase inversion (180-degree phase shift). This feedback signal opposes any changes in the input signal, reducing the overall gain and making the amplifier more predictable and linear.
The key features and benefits of negative feedback in op-amp circuits include:
Stability: Negative feedback improves the stability of the amplifier, ensuring that it remains well-behaved and avoids oscillations or other unwanted behavior. It helps in reducing distortion and noise.
Linearity: By reducing the gain at the expense of stability, negative feedback can help achieve a linear relationship between the input and output signals.
Input/Output Impedance Matching: Negative feedback tends to lower the input and output impedances of the amplifier, making it easier to interface with other circuits.
Bandwidth Control: Negative feedback can help control the bandwidth of the amplifier, which can be useful in certain applications where a limited bandwidth is desired.
The most common type of negative feedback used in op-amp circuits is voltage feedback, where a portion of the output voltage is fed back to the inverting (-) or non-inverting (+) input of the op-amp. The amount of feedback is determined by the feedback network (resistors, capacitors, etc.) connected between the output and the input.
In an ideal op-amp with negative feedback, the voltage at the inverting and non-inverting inputs is equal (a virtual short). This concept is known as the virtual ground, and it forms the basis for many op-amp circuit designs.
Overall, negative feedback is a powerful technique that helps achieve stable, linear, and well-controlled amplifier operation, making it a cornerstone of modern electronics design.