# Linear Integrated Circuit and Applications August 2005

Note: Answer any FIVE full questions.

1.  (a) What are the advantages of a differential amplifier over d.c. amplifier.

(b) Draw different stages of a typical op-amp and discuss their importance.

(c)  Draw the overall frequency response of an op-amp and explain how the stability gets affected when operated in closed loop.

2.(a) Define the following applied to one op – amp and give their typical values.

i)  Open loop gain

ii)  Unity cross-over frequency

iii)  Slow rate

iv)   Differential input impedance.

(b) An op.amp has to be used in pulse application at IQKHz. If this op-amp is operated with a power supply voltage of ±10 volts, calculate the slow rate.

(c)   Prove that an non-inverting amplifier can be used as an voltage follower.

3. (a) Draw a differentiator using op-amp and indicate the output that will be sean on a C.R.O. if the input given in 2.5 sin wt.

(b) It is proposed to rectify a sinusoidal signal with an amplitude of 100 microvolts. Suggest a circuit to get positive pulses at the output from negative input swings. Donot use more than one op-amp for a peak output of 5 Volts.

(c) Draw the circuit of an difference amplifier using an OP-amp, that gives an output Vq = Arc(Vi2 -Vfa) Calculate Arc in terms of circuit components.

4.  (a) Explain the importance of positive feedback in an op-amp comparator, by using transfer characteristic.

(b) Design a monostable that has – Vosa+ as the stable state. The quasi stable state of + V03af exists for 0.1 m sec. Assume /? = 0.25 Draw the waveforms at output, across capacitor and at non- investing terminal and also explain the operation.

5.  (a) What are data converters and where are they used, give typical examples.

(b) Draw the schematic of an 8-bit counter ramp ADC and explain its working.

(c)  What will be the converssion time if 1.25 volts is to be converted into binary code using circuit in 5(b) ? What will be the output code ? Given V{nmax — 5 Volts and clock frequency 10kHz.

6. (a) It is required to generate symmertical rectangular waves using a timer that has threshold voltage of \Vcc- Design the circuit for a frequency of 5000Hz. Draw waveforms at different points and explain the operation.

(b) Design an active BP filter having lower cutoff of 2.3KHz and upper cutoff of 5KHz. Draw the bandpass characteristic. Assume the filter is second order. Butterworth with a gain of 3.

7.  (a) Explain the working of a switching regulator by drawing circuit and waveforms.

(b) IC 723 has to be used to get an output of 2.5volts. Suggest the circuit and design circuit components. Explain the working of designed circuit for a maximum output current of 50mi.

(c) Explain why switching regulator is prefered over linear regulators.

8. Write short notes on :

a)  Offset characterstics

b)  Analog multipliers

c)   Phase locked loop

d)  Flash converter