JNTU
JNTU B.Tech III LINEAR AND DIGITAL IC APPLICATIONS Previous Question Paper (October - 2020 - R16)
Answer any five questions. All questions carry equal marks.
Main
Draw the basic circuit diagram of an Op-amp differentiator and explain its operation and stability.
Answer
An Op-amp differentiator circuit consists of an input capacitor C in series with the inverting terminal, and a feedback resistor R connected between the output and the inverting input. The non-inverting terminal is grounded.
The output voltage is given by the formula:
Operation: The input current flows through the capacitor, which is proportional to the rate of change of the input voltage. This current then flows through the feedback resistor, creating an output voltage proportional to the derivative of the input signal. As the frequency of the input signal increases, the gain of the differentiator increases, making it highly sensitive to high-frequency noise.
Stability: The circuit is inherently unstable at high frequencies because the gain increases linearly with frequency. This leads to noise amplification and potential oscillations. To improve stability, a small resistor is often added in series with the input capacitor, and a small capacitor is placed in parallel with the feedback resistor to create a low-pass filter effect, limiting the high-frequency gain.
What is voltage reference? Why it is needed?
Answer
A voltage reference is a precision electronic component designed to provide a stable, constant output voltage that remains independent of changes in power supply voltage, load current, temperature, or time.
It is needed for the following reasons:
- Data Conversion: In Analog-to-Digital (ADC) and Digital-to-Analog (DAC) converters, the reference voltage defines the full-scale range and resolution of the conversion process.
- Precision Measurement: It serves as the standard against which unknown voltages are compared in instrumentation and sensor circuits.
- Voltage Regulation: It acts as the stable baseline for linear and switching voltage regulators to maintain a constant output voltage for power supplies.
- Signal Processing: It provides a stable bias point for sensitive analog circuits, ensuring consistent performance despite fluctuations in the primary power source.
Draw the circuit diagram of an logarithmic amplifier using op-amps and explain its operation.
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Discuss the limitations of linear voltage regulators.
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Define an all-pass filter. How can it be justifiably called as phase shift circuit?
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Explain the operation of Square Wave Generation.
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Draw the block diagram of 565 PLL and explain about each block. Make circuit connections to track the input signal and explain its operation.
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Draw the circuit of Schmitt trigger using 555 timers and explain its operation.
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Explain Four bit binary input D/A converter with a neat circuit.
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Explain working of R/2R D/A converter with a neat circuit.
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Explain Successive Approximation ADC with its block diagram.
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Write about Basic DAC techniques.
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Find the logic output of a TTL NAND gate that has all its inputs unconnected.
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Design a full subtractor with NAND gates.
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Design a 4-bit binary synchronous counter using 74×74.
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Explain the S-R and J-K flip flops with truth table.
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