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Question

A constant negative DC voltage is applied to the input of an inverting integrator. Assuming the op-amp starts at zero volts and remains unsaturated, the output will be:

The correct answer is

A positive-going linear ramp

An inverting integrator uses an op-amp with a resistor R at the input and a capacitor C in the feedback path. Exploiting the virtual-ground at the inverting input, the input current Vin/R must flow into the capacitor, producing the classic integrator relation:

Vout(t) = −(1/RC) ∫ Vin dt + Vout(0)

The output rate of change (slope) is dVout/dt = −Vin/(RC), so a constant input yields a constant slope — a straight-line ramp.

Here Vin is a constant negative DC voltage, Vin = −V (V > 0), and the output starts at zero:

Vout(t) = −(1/RC) × (−V) × t = +Vt/(RC)

  • The double negation — inverting integrator acting on a negative input — gives a positive slope.
  • Because RC is constant, the slope is constant, so the trace is a straight positive-going linear ramp rising steadily from zero (until the op-amp eventually approaches saturation, which the problem excludes).

The other options do not fit. A negative-going ramp would result only from a positive DC input; here the input is negative, so the slope flips to positive. A constant DC output would require the input to be zero (no charging current), which is not the case. A square wave cannot arise from integrating a steady DC level, since integration of a constant is inherently a linear ramp, not an abruptly switching waveform.

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Similar Questions

  1. The current flows directly into the input terminals of an ideal op-amp is _____________ due to ____________ input impedance.

  2. An op amp acting as a comparator typically operates in:


Important Questions from Op-Amp and Its Applications

  1. Identify the circuit which is not the application of op-amp.

  2. A circuit whose output is proportional to the difference between the input signals is considered to be which type of amplifier?

  3. What is the ideal input resistance of an Op-amp (operational amplifier)?

  4. Which of the following Op-Amp (operational amplifier) circuit configurations primarily operates in a non-linear mode?

  5. Which type of multivibrator is commonly used for pulse stretching or generating a single output pulse of a predetermined duration upon receiving an input trigger?

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