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A current controlled current source (CCCS) has an input impedance of 10 Ω and output impedance of 100 kΩ. When this CCCS is used in a negative feedback closed loop with a loop gain of 9, the closed loop output impedance is

1. 10 Ω
2. 100 Ω
3. 100 kΩ
4. 1000 kΩ

Correct answer: 1000 kΩ

Solution

In a negative feedback system, the closed loop output impedance is significantly increased by the loop gain. Given the output impedance of the CCCS is 100 kΩ and the loop gain is 9, the closed loop output impedance becomes 100 kΩ multiplied by (1 + loop gain), resulting in 100 kΩ * 10 = 1000 kΩ.

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