Positive and Negative Feedback Amplifier: Difference

What is Positive Feedback Amplifier ?

A positive feedback amplifier is a circuit in which a fraction of the output voltage is fed back to the input with the same polarity, reinforcing the input signal. This regenerative feedback results in an increase in the overall gain of the amplifier. Positive feedback amplifiers are characterized by their ability to boost signal amplitudes and sensitivity. However, they are prone to instability, oscillations, and saturation due to the cumulative reinforcement of the input signal. Positive feedback amplifiers are commonly employed in applications like oscillators, where sustained oscillations are desired, or in circuits where intentional distortion and nonlinearity are required, such as in Schmitt triggers and relaxation oscillators.

What is Negative Feedback Amplifier?

A negative feedback amplifier is a circuit in which a portion of the output voltage is fed back to the input with an inverted (negative) polarity, opposing the input signal. This degenerative feedback serves to stabilize and control the amplifier’s performance by reducing gain, minimizing distortion, and improving linearity. Negative feedback amplifiers are widely used in various applications, including audio amplifiers and instrumentation amplifiers, where accuracy and fidelity are crucial. By trading some gain for increased stability and reduced distortion, negative feedback amplifiers provide a more predictable and controlled amplification process. This type of feedback helps maintain desired operating conditions and enhances the overall performance and reliability of the amplifier circuit.

Difference between Positive and Negative Feedback Amplifier


Sr. No.ParameterPositive Feedback AmplifierNegative Feedback Amplifier
1.Feedback TypePositive feedback (regenerative)Negative feedback (degenerative)
2.PurposeIncreases gain and sensitivityReduces distortion, improves stability, and accuracy
3.StabilityProne to instability and oscillationsEnhances stability and reduces oscillations
4.GainCan have high gain, may lead to saturation or distortionGain is controlled and more stable
5.Frequency ResponseCan lead to narrow or wideband frequency responseTends to have a more uniform and predictable response
6.DistortionMay introduce distortion and nonlinearitiesReduces distortion and improves linearity
7.ApplicationsOscillators, amplifiers with intentional distortionAudio amplifiers, instrumentation amplifiers
8.Sensitivity to Parameter ChangesHighly sensitive to component variationsMore robust and less sensitive to component variations
9.NoiseAmplifies noise along with the signalReduces noise and improves signal-to-noise ratio
10.Circuit ComplexityOften simpler in circuit designTypically more complex due to feedback network
11.Circuits ExamplesSchmitt triggers, relaxation oscillatorsOperational amplifiers, voltage regulators
12.Common Mode Rejection RatioGenerally lower CMRR due to higher gainHigher CMRR due to controlled gain and better linearity
Positive and Negative Feedback Amplifier


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