Linear Integrated Circuits and Applications

In a monolithic IC fabrication process, boron diffusion is carried out for 2 hours at 1100°C. If the diffusion coefficient increases exponentially with temperature, which fabrication parameter primarily controls junction depth?

1. Oxide capacitance
2. Diffusion time and temperature
3. Metal interconnect thickness
4. Crystal orientation only

An ideal operational amplifier with open loop gain 10⁶ is connected in a non-inverting configuration having R_f = 90kΩ and R₁ = 10kΩ. The closed loop gain is closest to

1. 1
2. 9
3. 10
4. 100

A practical differentiator using OP-AMP becomes unstable at high frequencies mainly because of

1. Excessive gain for high frequency noise
2. Infinite slew rate
3. Very low input impedance
4. Infinite bandwidth

In an instrumentation amplifier, the major purpose of using three OP-AMPs is to obtain

1. Low bandwidth
2. High output resistance
3. Low slew rate
4. High CMRR with high input impedance

A 4-bit R-2R ladder DAC uses reference voltage of 8V. The analog output corresponding to digital input 1010 is

1. 5V
2. 5V
3. 6V
4. 5V

The free running frequency of a 555 timer in astable mode primarily depends upon

1. External R-C network
2. Comparator offset voltage
3. Output transistor gain
4. Supply ripple factor

The main function of a Phase Locked Loop IC 565 in communication systems is

1. Voltage amplification
2. Frequency synthesis and synchronization
3. Current limiting
4. Rectification

An LM317 regulator is adjusted using external resistors. If the adjustment terminal becomes open, the output voltage generally

1. Becomes zero
2. Becomes fixed at 5V
3. Rises toward maximum regulated value
4. Oscillates at high frequency

A second order active low pass filter has cut-off frequency 1kHz. If the input frequency is increased to 10kHz, the output magnitude will

1. Attenuate significantly
2. Remain unchanged
3. Increase exponentially
4. Become unstable immediately

The ICL8038 IC is widely used for generating

1. PWM pulses only
2. RF carrier modulation only
3. Square, triangular and sine waves
4. Digital clock synchronization only

Explain the complete monolithic IC fabrication process including epitaxial growth, masking, etching and diffusion techniques.

Discuss briefly operation of comparators, multivibrators and waveform generators using OP-AMPs, and design a Schmitt trigger circuit using V_sat = ±12V such that the upper trigger point is 4V and lower trigger point is 2V. Determine suitable resistor values.

Discuss the construction and fabrication of monolithic resistors, capacitors and FETs in integrated circuits, and determine the sheet resistance and capacitance value for a fabricated IC structure having resistive layer resistivity ρ = 0.02Ωm, thickness 2μm, resistor dimensions 200μm×20μm, dielectric constant ε_r = 3.9, oxide thickness 0.1μm, and capacitor plate area 100μm×100μm.

Explain the working of DAC and ADC circuits using operational amplifiers including weighted resistor.

Describe ideal and practical characteristics of an operational amplifier including offset voltage, bias current, slew rate and CMRR, and calculate the closed loop gain and bandwidth of an amplifier having open loop gain 2×10⁵ and unity gain bandwidth of 2 MHz.

Explain the internal functional blocks and operating modes of IC 555 timer with suitable diagrams, and design an astable multivibrator using 555 timer to generate a 5 kHz square wave with duty cycle 60%.

Explain the working principle of inverting and non-inverting amplifiers using OP-AMP with neat circuit diagrams and design an amplifier system that produces output V_o = −5V₁ + 3V₂ for given input voltages using suitable resistor selection.

Describe the working principle and applications of PLL IC 565 and voltage controlled oscillator IC 566, and calculate the lock range and capture range of a PLL system having free running frequency 100 kHz, loop gain K=104, and supply voltage 12V.

Discuss the operation and limitations of integrator and differentiator circuits using operational amplifiers, and design a practical integrator circuit for a square wave input of amplitude 4V and frequency 2 kHz to obtain a triangular wave output of peak amplitude 5V.

Explain the operation of fixed and variable IC voltage regulators including LM78XX, LM79XX and LM317 with protection mechanisms, and design a regulated power supply producing variable output from 5V to 15V using LM317.

Explain the construction and working of instrumentation amplifiers with emphasis on CMRR improvement and noise rejection, and design a three OP-AMP instrumentation amplifier having overall gain 100 using R₁ = R₂ = 10kΩ. Determine the value of gain-setting resistor R_G.

Discuss the architecture and applications of SMPS and LM380 power amplifier IC with suitable block diagrams, and calculate the efficiency, ripple factor and power dissipation of a switching regulator having input voltage 24V, output voltage 12V, output current 2A, and input power 30W.

Describe first and second order active filters using operational amplifiers and compare Butterworth and Chebyshev responses, and design a second order low pass Butterworth filter with cut-off frequency 5 kHz, gain 2, and capacitances C₁ = C₂ = 0.01μF. Determine the required resistor values.

Explain the differential amplifier configuration used in operational amplifiers with proper circuit analysis, and determine the differential gain, common mode gain and CMRR for a transistor differential pair having differential gain A_d = 5000 and common mode gain A_c = 0.5.

Limitations of practical operational amplifiers in high frequency applications and methods for compensation

Comparative analysis of weighted resistor DAC and R-2R ladder DAC in high resolution systems

Design challenges in high precision active filters and instrumentation amplifiers for biomedical applications

Role of PLL and function generator ICs in modern communication and embedded systems