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A feedback amplifier is an electronic amplifier that uses feedback to enhance its performance. Feedback is basically a process in which some part of the output signal of an amplifier is fed back to the input. This can be used in both analog and digital circuits, but we will consider the analog point of view here.
In a feedback amplifier, the feedback can be either positive or negative. The distinction is crucial:
A typical feedback amplifier circuit consists of:
Input Signal (Vi): The signal that needs amplification.
Output Signal (Vo): The amplified signal.
Feedback Network: A network of resistors, capacitors, or other components that determines the proportion of the output signal to be fed back to the input. This network is responsible for setting the amplifier's characteristics.
Voltage Feedback (Series-Shunt Feedback): The feedback is proportional to the output voltage.
Current Feedback (Series-Series Feedback): The feedback is proportional to the output current.
Shunt-Series Feedback: The feedback network is connected in parallel with both the input and output.
Shunt-Shunt Feedback: The feedback network is connected in shunt with the input and series with the output.
Improved Stability: Negative feedback reduces the gain variations due to changes in components' parameters or external factors.
Reduced Distortion: It minimizes the signal distortion caused by the amplifier's nonlinear characteristics.
Increased Bandwidth: It extends the frequency range over which the amplifier can operate effectively.
Controlled Gain: The overall gain of the amplifier becomes more predictable and can be set accurately by the feedback network.
Improved Impedance Characteristics: It can increase the input impedance and decrease the output impedance, which is often desirable in amplifier design.
Amplifier feedback is employed extensively in most electronic devices and systems to attain the specified performance parameters:
Overall, feedback amplifiers contribute significantly to electronics technology in terms of enhanced performance and stability. Their features of controlling gain, increasing bandwidth, and minimizing distortion make them very useful in different applications.
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