Question

The figure shows an opamp circuit with a 5.1 V Zener diode in the feedback loop. The opamp runs from \( \pm 15 \, {V} \) supplies. If a \( +1 \, {V} \) signal is applied at the input, the output voltage (rounded off to one decimal place) is:

 

Hint:

In circuits with Zener diodes, the voltage across the diode remains constant when it is in its breakdown region. This is used to clamp the output voltage to a specific value.

Answer 1

Correct Answer: 7

Step 1: In the given op-amp circuit, the Zener diode is in the feedback loop with a breakdown voltage of 5.1 V. The Zener diode operates in the breakdown region, which means the voltage across it will be clamped to 5.1 V, regardless of the output voltage of the op-amp. Step 2: The op-amp operates in the linear region, and the voltage across the Zener diode remains constant at 5.1 V. The input voltage is \( +1 \, {V} \), and since the op-amp is configured in a feedback loop, the output voltage will be adjusted to maintain the voltage across the diode at 5.1 V. Step 3: Since the Zener diode has a voltage of 5.1 V, the output voltage will be clipped at \( +5.1 \, {V} \). Therefore, the output voltage of the op-amp is: \[ V_{{out}} = 7.2 \, {V}. \]