What do you understand by feedback in amplifier? Explain its types. Write two advantages and disadvantages of negative feedback.

Feedback in Amplifiers

Feedback in amplifiers is a process in which a portion of the output signal is fed back to the input of the amplifier. This feedback can be either positive or negative.

Positive Feedback:

In positive feedback, the output signal is fed back to the input in-phase with the input signal. This causes the amplifier to amplify the input signal even more, resulting in a further increase in the output signal. This process continues until the amplifier reaches saturation.

Positive feedback is used in oscillators to generate a continuous oscillating signal.

Negative Feedback:

In negative feedback, the output signal is fed back to the input out-of-phase with the input signal. This causes the amplifier to reduce the gain of the input signal, resulting in a decrease in the output signal. This process continues until the output signal is equal to the input signal.

Negative feedback is used in amplifiers to improve the stability, linearity, and bandwidth of the amplifier.

Types of Feedback:

There are two main types of feedback in amplifiers:

• Voltage feedback: In voltage feedback amplifiers, the feedback signal is taken from the output voltage of the amplifier.
• Current feedback: In current feedback amplifiers, the feedback signal is taken from the output current of the amplifier.

Advantages of Negative Feedback:

• Increased stability: Negative feedback reduces the gain of the amplifier, which makes the amplifier less sensitive to changes in the input signal and the amplifier's internal parameters.
• Improved linearity: Negative feedback reduces the distortion of the output signal, making the amplifier more linear.
• Increased bandwidth: Negative feedback extends the bandwidth of the amplifier, allowing it to amplify a wider range of frequencies.

Disadvantages of Negative Feedback:

• Reduced gain: Negative feedback reduces the gain of the amplifier, which can make it difficult to achieve the desired output signal level.
• Increased noise: Negative feedback can increase the noise level of the amplifier, making it more difficult to distinguish the input signal from the noise.