Andhra University BE/B.Tech Electronics-II Previous Paper 2006
- Answer ALL questions.
(a) Why the band width of an feedback amplifier should increase with negative feedback?
(b) State the effect of current shunt on the input and output impedences of an amplifier.
(c)It is desired to have an ossilator at 10khz. Do you use Rc type or Lc type?Justify.
(d) State the advantages of crystal controlled ossilators.
(e) Why differentiator circuits using operational amplifiers are not preffered in circuits?
(f) What is the order of “offset voltage” and “offset current” for a micro A 741 operational amplifier? Give reasonable values.
(g) What is “resolution“of a binary?
2.(a)Prove that the negative feedback in amplifiers reduces distortion.State the assumptions made in your derivation. (6)
(b)An amplifier has an open loop voltage gain of 1000 and an output impedence of 10kohms.It is desired to reduce the output impedence to 1kohms using negative feedback.Suggest the type of feedback to be used and the feedback factor. Detyermine the voltage gain of the amplifier with feedback. (8)
3.(a) For the two stage feedback amplifier shown in figure 1.0,determine (i)AVj=VO/VS (II) AIJ=IO/IS, (iii) Rif and (iv)Rof. Assume that the transistors are identical and have the following parameters. Hie=2kiohms,hfe=0 and hoe=0. (10)
(b)Explain the parameters on which the amplitude and frequency stability of an ossilator depend. Justify your answer with reasons. (4)
4. (a) Draw the circuit diagram of an Hartley oscillator and explain how the barkhausen conditions are satisfied. Derive the expression for the frequency of oscillations and conditions for oscillations. (6)
(b) Design a wein bridge oscillator to obtain a 5kohm sinusoidal wave form.Show the circuit with all the component values.Give its design equations and derive them. (8)
5. (a) Explain with neat diagrams how the following parameters of an operational amplifier are measured?
(ii)Slew rate and
(b) Realise (i)an invertor amplifier and (ii) anon inverting amplifier using operational amplifiers both providing a voltage gain 10. Compare them with reference to input impedence and error in the output voltage due finite CMRRof 60 Db. (5)
6.(a) An operation amplifier with c=0.1 micro F and R=100kohms is to be used to produce a linear lamp of amplitude 10 volts and of duration 100 milli seconds.What is the minimum value of open loop gain of the operational amplifier to ensure that the departure from the linearity of the ramp is less than 0.1%? (8)
(b)Explain with a neat circuit diagram how do you minimize the offset voltage in a non inverting amplifier. (6)
7. (a)Explain how an astable multivibrator can be used as avoltage controlled oscillator.(50
(b) Design a monostable multivibrator to produce a pulse of 10 milli seconds.Use transistors having VCE(sat)=0V,VBE(sat)=0.6V,VBE(CUTOFF)=0V and hFE=80. Choose VCC==10V,VBB=-10V and IC(sat)=2 mA.Show the circuit with all the components and explain its operation with the wave forms seen at both the collectors and bases. (9)
8.(a) Distinguish between symmetrical and unsymmetrical triggering in multivibrators. When do you prefer one over the other? Justify. (5)
(b) Draw the circuit diagram of a self biased distable multivibrator and explain iots operation waveforms.State its advantages over fixed bias bistable multivibrator with relevant.(9)http://www.stepinau.com/2013/10/31/andhra-university-beb-tech-electronics-ii-2006/CSE 2.2 SyllabusCSE,CSE 2.2 Previous Papers,CSE Previous Papers,Discrete Electronics-II Previous Papers,IT,IT 2.2 Previous Papers,IT Previous Papers