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GATE 2015 EE (EE2) – Question 49

Analog and Digital Electronics · Operational amplifiers: characteristics and applications · 2 marks · Multiple choice

The ideal op-amp saturates at ±10 V. In steady state its output v0 is

Diagram for GATE 2015 EE (EE2) question 49
  1. square wave, period 0.55 ms
  2. triangular wave, period 0.55 ms
  3. square wave, period 0.25 ms
  4. triangular wave, period 0.25 ms

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Correct answer: (A) square wave, period 0.55 ms

Explanation

Equal 2 kΩ divider resistors set the switching thresholds at ±5 V. The capacitor charges toward the current ±10 V output through 1 kΩ.

For a half-cycle rising from −5 to +5 toward +10, $t=RC\ln[(10+5)/(10-5)]=RC\ln3$. With C=0.25 μF, the full period is 2RC ln3=0.549306 ms.

The op-amp output itself switches between saturation levels and is a **square wave of period about 0.55 ms, A**. The capacitor waveform is exponential, not the output asked for.

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