**JNTU PAPERS**

**JNTU, B.Tech,I-Semester Linear And Digital Ic Application November 2008**

**( Computer Science & Engineering, Information Technology and Computer Science & Systems Engineering) SET-3**

** **

1. (a) Why is emitter resistor RE replaced by a constant current bias circuit in differential amplifier stage of an OP-AMP? [3]

(b) Explain why open loop configurations are not used in linear applications [4]

(c) For an OP-AMP, PSRR=70dB(min),CMRR=105,differential mode gainAd=105.

The output voltage changes by 20V in 4 microseconds. Calculate i)numerical

value of PSRR ii) Common mode gain iii) Slew rate of the OP-AMP. [9]

2. (a) Define slew rate and derive the expression for it. List causes of the slew rate

and explain its significance in applications [10]

(b) Explain the difference between slew rate and transient response [6]

3. (a) What feedback is preferred for oscillators and why? What is the effect of

negative feedback? [8]

(b) Design an OP-AMP based relaxation oscillator and derive the frequency of

oscillation. [8]

4. (a) Explain the operation of Monostable multivibrator using 555 timer. Derive

the expression of time delay of a Monostable multivibrator using 555 timer.

[10]

(b) Design a Monostable multivibrator using 555 timer to produce a pulse width

of 100 m sec. [6]

5. (a) Give the functional block diagram of NE 565 PLL (DIP) and for the given

component values. C1 = 390PF, C2 = 680PF and R1 = 10k, Vcc = ±6V

Find [8]

i. The free running frequency

ii. The lock range and capture range

Where C1 is the capacitor connected between pin number 9 and ?VCC , C2 is

the capacitor connected between +VCC and output pin 7, and R1 is connected

between pin number 8 and +VCC

(b) Give the functional block diagram of VCO NE566 and explain its working and

necessary expression for free running or center frequency. [8]

6. (a) Explain the design procedure (with suitable circuit diagram of a fourth order

Butterworth low-pass filter). [10]

(b) A certain narrow band-pass filter has been designed to meet the following

specifications: fC=2kHz. Q=20, and Ap=10. What modifications are neces-

sary in the filter circuit to change the center frequency ‘fc’ to 1kHz, keeping

the gain and band-width constant? [6]

7. (a) What is meant by Tri-state logic ? Draw the circuit of Tri-state TTL logic

and explain its functions. [8]

(b) Draw the circuit of ECL logic OR/NOR gate and explain its functions. [8]

8. (a) Draw the circuit of a Weighted Resistor DAC and obtain expression for n-bits.

(b) Sketch the Analog output voltage for the given digital input code. [4]

(c) What are the major disadvantages in this type