Related InterviewSolutions

• Determine the conductivity of pure germanium at `27^(@)C`. The concentration of the carriers at this temperature is `2.2 xx 10^(19)m^(-3)`. The mobility of electrons = 0.36 and that of holes = 0.17
• The plate resistance of a triode is `7.7 kOmega`, and the transconductanace is 2.6 millimho. If only the plate voltage is increased by 50 V, what is the increase in the plate current ? What change in grid voltage will now bring the plate current to its former value ?
• The voltage of a triode amplifier with a resistive load of `5 kOmega` is 10 while with a resistive load of `12 kOmega`. It is 15. Calculate the amplification factor and plate resistance of the triode.
• In the accompanying circuit (Fig. 5.9) the value of `beta` is `100`. Find `I_(B),V_(CE),V_(CE)` and `V_(BC)`, when `I_(C) =1.5 mA`. Is the transistor in active, cut-off or saturation state ?
• In a transistor collector load is `4 kOmega` whereas the zero signal current is 1 mA. (a) What is the operating point if `V_(C C) = 10 V` ? (b) What will be the operating point if `R_(L) = 5 kOmega` ? [Hint : Operating point is zero signal collectorm current and `V_(CO)`]
• In triode valve, for a grid voltage `V_(g) = -1.2 V`, the plate current `I_(p)` (in mA) ad the plate voltage are given by the relation `I_(p) = -50 +0.1 V_(p)`, when the grid voltage is changed to `-3.2 V` and the plate voltage is kept at 150 V, plate current of 5 mA is observed. Calculate the valve constant and the voltage amplification for `20 k Omega` load in the plate circuit.
• A transistor connected in common emitter configuration has `V_(C C)=8V, V_(L) = 0.5 V` and `R_(L) = 800 Omega`. If its `alpha = 0.96` determine (i) collector emitter voltage, (ii) its base current.
• The base current of a transistor is `105 muA` and the collector current is 2.05 mA. Determine the alue of `beta,I_(C) and alpha`. If a change of `27 muA` in the base current produces a change of 0.65 mA in the collector, find `beta_(ac)`.
• Assume that the silicon diode in the given circuit requires a minimum current of 1 mA to be above the (knee-point voltage = 0.7 V) of its `I-V` characteristics. Assuming that the voltage across the diode is independent of current above the knee-point, find the maximum value of R so that the voltage is above the knee-point if `V_(B) = 5A`. Also find the value of R to establish a current of 5 mA in the circuit for the since voltage.
• In a silicon transistor the base current is changed by `20 mu A`. This results in a change of 0.02 V in the base to emitter voltage and a changed of 2 mA in the collector current (a) Find the input resistance `r_(b),beta_(ac)` and transconductance `g_(m)` of the transistor (b) The transistor is used as an amplifier with a load resistance of `5 kOmega`. What is the voltage gain of the amplifier ?