STM

this is STM paper......

>> i'll use ot as notation for multiple choice,
>> i m not writing the choices-
>>
>> 1. in a VCO,the capacitance is varied by  using
>__________.
>>    ans:rev biased varactor diode.(ot)
>>
>> 2. a pnp trans. in active region has  _____________.
>>   ans:b-e junction fwd biased & b-c rev biased.(ot)
>>
>> 3. in a nmos how is V-threshold affected by increasing
>>    doping conc. of substrate ?(ot)
>>    ans:increases
>>
>> 4. condition for sustained oscillations in a osc.
>is___.
>>    ans:A=1 & phase shift = n*pi.(ot)
>>
>> 5. if  A?B=C and C?A=B then what is the boolean
>operator ?
>>    ans:xor (ot)
>>
>> 6. clk is given with some period T to a logic gate.
>>    the same clk is again fed to the gate via a delay
>>    element with a delay of T/4 duration.if the gate
>>    acts as a freq.doubler then identify the gate.
>>    ans:xor (ot)
>>
>> 7. define the setup time & hold time in a f/f.
>>
>> 8. given a D f/f ,construct a T f/f from it.
>>
>> 9. the following ckt(LADDER) with each resistance
>equal
>>    to R(=10 OHMS) is given,find the value of
>resistance
>>    between A & B
>>
>>     A___________R_________R____
>>   |          |        |
>>           R          R        R
>>           |          |        |
>>     B___________R_________R____
>>
>>    ans:R<10 OHMS (ot)
>>
>> 10. in the given ckt,find the current in R1 resistor.
>>     assuming a gnd somewhere(i don't remember
>exactly!)
>>
>>     ____R=10____              _____R=10_____
>>     |           |             |            |
>>     |           |             |            |
>>    +          R=5            R=10          +
>>    V=10v        |             |           V=20v
>>    -            |             |            -
>>    |____________|_____R1=5____|____________|
>>
>>
>> 11. the BW of a communication channel is 10kbps,
>>     what does this mean ?choices--
>>     (a)the data rate can never exceed 10kbps
>>     (b)can be exceeded using level 4 modulation
>>     (c)"   "    "        "     "   2    "
>>
>> 12. given a 2:1 mux,how will u implement an AND & OR
>gate ?
>>
>> 13. a triangular wave with equal excursions in +ve &
>-ve direction
>>     & with voltages marked V1 & V2 is given as input
>to the
>>     following clipper ckt. having 2
>>     diodes ,find o/p.
>>
>>     _________R________________
>>                 |        |
>>                 +        -
>>                 D        D
>>                 -        +
>>    Vin          |        |      Vo
>>                 +        +
>>                 V1       V2
>>                 -        -
>>     ____________|________|_____
>>
>>
>> 14. find vo in the given ckt when switches r closed
>at t=0
>>     all caps r of 1 farad,cap1 initially charged to
>4v,cap2
>>     to 3v & cap3 to 2v,vo is voltage across cap3
>>
>>     _________/________/_____________
>>     |      |      |          |
>>     V     CAP1   CAP2      CAP3    vo
>>     |______|______|__________|______
>>
>>
>> 15. a trans. with Re resistor is given,hfe,hie values
>r
>>     given required to find i.p resistance . (ot)
>>     ans:200k (not sure)
>>
>> 16. a ckt with 2 d f/f is given ,both have same clk,
>>     o/p of 2nd f/f say d2 is inverted & fed back to
>it.
>>     the i/p to d1 comes by exoring d1's o/p with the
>>     complemented o/p of d2,identify the ckts
>operation.
>>     ans:the ckt is a counter with 3 states(0,1 & 3)
>>         states not sure please check out.
>>
>> 17. a trans. ckt with npn ,Re & Rc is given ,Ic or Ib
>>     is asked. (ot)
>>
>> 18. an instrumentation amplifier ckt with 2 op amps is
>>     given,vin is a sine wave,o/p of upper op amp is v1
>>     that of lower one is v2,& v3 is v1 connected to v2
>>     wrt gnd.u'll be asked to draw waveforms for v1,v2
>>     & v3 on the question paper itself.(6 marks)
>>
>> 19. an amp (block dig.) with a f/b which introduces
>>     -45db attenuation is given,gain plot is given,u r
>req.
>>     to plot the phase plot & comment on stability of
>the
>>     system.(6 marks)