JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III LINEAR IC APPLICATIONS Previous Question Paper (September - 2021 - R15)
Answer any five questions. All questions carry equal marks.
Main
Explain the operation of an op amp in inverting amplifier mode and derive expression for voltage gain for it.
Answer
In an inverting amplifier, the non-inverting terminal is connected to ground, and the input signal is applied to the inverting terminal through an input resistor R1. A feedback resistor Rf is connected between the output and the inverting terminal. Due to the virtual ground concept at the inverting input, the voltage at this node is 0V. Applying Kirchhoff's Current Law at the inverting node:
Rearranging the terms to solve for the voltage gain (Av = Vout / Vin):
The negative sign indicates a 180-degree phase shift between the input and output signals.
Define the DC and AC characteristics of an op amp. List their ideal values.
Answer
DC characteristics describe the behavior of an op-amp under static conditions, while AC characteristics describe its performance with time-varying signals.
DC Characteristics:
- Input Bias Current: The average of the currents flowing into the two input terminals. Ideal value: 0 A.
- Input Offset Current: The difference between the currents flowing into the two input terminals. Ideal value: 0 A.
- Input Offset Voltage: The voltage required at the input to make the output zero. Ideal value: 0 V.
- Thermal Drift: The change in offset voltage or current per degree Celsius. Ideal value: 0.
AC Characteristics:
- Slew Rate: The maximum rate of change of output voltage per unit time. Ideal value: Infinity.
- Gain Bandwidth Product (GBW): The product of open-loop gain and bandwidth. Ideal value: Infinity.
- Common Mode Rejection Ratio (CMRR): The ratio of differential gain to common-mode gain. Ideal value: Infinity.
- Input Impedance: The impedance seen looking into the input terminals. Ideal value: Infinity.
- Output Impedance: The impedance seen looking into the output terminal. Ideal value: 0 Ω.
Draw the sample and hold circuit and explain its operation.
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Explain how an op amp used as a adder.
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Design an op amp differentiator that will differentiate an input signal with fmax=100Hz. Draw the output waveform for a sine wave of 1V peak at 100Hz applied to the differentiator. Also draw the output waveform for square wave input.
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Explain how an op amp is used an astable multivibrator. Derive an expression for frequency of oscillation.
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Draw quadrature oscillator circuit and explain its operation.
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How can you obtain a BPF from LPF and HPF? Draw the block schematic.
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Explain the operation of 555 timer in monostable mode.
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Discuss any two applications of 555 timers in monostable mode.
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With suitable schematic, explain how a R-2R ladder network converts a digital signal into analog from equivalent.
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Define lock range and capture range of PLL.
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Explain the operation of successive approximate type ADC with an example.
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Write a short note on application of V/I converter.
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Describe the operation of the dual slope integrating Analog to Digital converter.
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Compare flash type, integrating type and successive approximation type ADCs in terms of conversion time and accuracy.
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