Multiple choice

In the following limiter circuit, an input voltage Vi = 10 sin 100 $\pi$t is applied. Assume that the diode drop is 0.7 V when it is forward biased. The zener breakdown voltage is 6.8 V. The maximum and minimum values of the output voltage respectively are

  1. 6.1 V, - 0.7 V

  2. 0.7 V, - 7.5 V

  3. 7.5 V, - 0.7 V

  4. 7.5 V, - 7.5 V
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C Correct answer
Explanation

For the positive half of $V_i,$ the diode $D_1$ is forward bias, $D_2$ is reverse bias and the zener diode is in breakdown state because state because $V_i > 6.8$

Thus output voltage is $V_0 = 0.7 + 6.8 = 7.5V$

For the negative half of $V_i$, $D_2$ is forward bias thus

Then $V_0 = -0.7 V$

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