The input impedance of an amplifier increases by the introduction of feedback. It is due to:
(a) Positive feedback
(b) current series negative feeeback
(c) current shunt negative feedback
(d) voltage shunt negative feedback?

Question

Answer

Understanding Feedback in Amplifiers
Feedback is a crucial concept in amplifier design that can significantly affect the input impedance of the circuit. When feedback is introduced, it can alter the amplifier's performance, including its input impedance.
Types of Feedback
- Positive Feedback:
- This type of feedback tends to increase the gain of the amplifier, potentially leading to instability and oscillation. It does not increase input impedance.
- Negative Feedback:
- Negative feedback is used to stabilize the gain and improve linearity. There are different configurations of negative feedback:
- Current Series Negative Feedback:
- This configuration typically lowers the input impedance because it introduces a series resistor, which increases total resistance.
- Current Shunt Negative Feedback:
- Similar to current series feedback but affects output impedance rather than input impedance. It does not increase input impedance.
- Voltage Shunt Negative Feedback:
- This configuration increases the input impedance. By providing feedback that reduces the voltage across the input terminals, it effectively raises the overall impedance seen by the source.
Conclusion
The increase in input impedance of an amplifier due to feedback is primarily attributed to voltage shunt negative feedback (d). This configuration enhances the amplifier's performance by allowing it to handle higher input resistance, making it suitable for various applications where high input impedance is essential.

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