Question

Q1(a) [2 Marks] Consider the simplified BJT amplifier circuit of Fig Q1(a) below. State, giving reasons, the type of common configuration employed if Vs is the input signal and Vo is the output signal. (Note: Bias network omitted for simplicity). Q1(b) Vs E B Fig Q1(a) lo C RL VO [7 Marks] The diagram of Fig Q1(b) below represents the small-signal h-parameter circuit of a certain Common Emitter (CE) amplifier. Derive an expression for the current gain A? = i?/ib for this circuit. Vbe Q1(c) B ib C 11 iL hie hfeib 1/hoe Zin RL Vce hreVce E Fig Q1(b) [2 Marks] For the circuit of Fig Q1(b), assume RL = 2k?, hre= 10??, hoe = 12µS, hfe = 100 and hie = 1k?. Using these values, calculate the current gain Ai. Q1(d) [7 Marks] For the circuit of Fig Q1(b), derive an expression for the voltage gain Av = Vce/Vbe. Q1(e) [2 Marks] Assuming the circuit has the same values as described by Q1(c) above, calculate the voltage gain Av for this circuit. Q1(f) [5 Marks] For the CE circuit of FigQ1(b) above, derive an expression for the input impedance Zin and hence calculate its value based on the values described in Q1(c) above.

          Q1(a)
[2 Marks]
Consider the simplified BJT amplifier circuit of Fig Q1(a) below. State, giving reasons, the
type of common configuration employed if Vs is the input signal and Vo is the output signal.
(Note: Bias network omitted for simplicity).
Q1(b)
Vs
E
B
Fig Q1(a)
lo
C
RL VO
[7 Marks]
The diagram of Fig Q1(b) below represents the small-signal h-parameter circuit of a certain
Common Emitter (CE) amplifier. Derive an expression for the current gain A? = i?/ib for this
circuit.
Vbe
Q1(c)
B
ib
C
11
iL
hie
hfeib
1/hoe
Zin
RL
Vce
hreVce
E
Fig Q1(b)
[2 Marks]
For the circuit of Fig Q1(b), assume RL = 2k?, hre= 10??, hoe = 12µS, hfe = 100 and hie = 1k?.
Using these values, calculate the current gain Ai.
Q1(d)
[7 Marks]
For the circuit of Fig Q1(b), derive an expression for the voltage gain Av = Vce/Vbe.
Q1(e)
[2 Marks]
Assuming the circuit has the same values as described by Q1(c) above, calculate the voltage
gain Av for this circuit.
Q1(f)
[5 Marks]
For the CE circuit of FigQ1(b) above, derive an expression for the input impedance Zin and
hence calculate its value based on the values described in Q1(c) above.

Q1(a)
[2 Marks]
Consider the simplified BJT amplifier circuit of Fig Q1(a) below. State, giving reasons, the
type of common configuration employed if Vs is the input signal and Vo is the output signal.
(Note: Bias network omitted for simplicity).
Q1(b)
Vs
E
B
Fig Q1(a)
lo
C
RL VO
[7 Marks]
The diagram of Fig Q1(b) below represents the small-signal h-parameter circuit of a certain
Common Emitter (CE) amplifier. Derive an expression for the current gain A? = i?/ib for this
circuit.
Vbe
Q1(c)
B
ib
C
11
iL
hie
hfeib
1/hoe
Zin
RL
Vce
hreVce
E
Fig Q1(b)
[2 Marks]
For the circuit of Fig Q1(b), assume RL = 2k?, hre= 10??, hoe = 12µS, hfe = 100 and hie = 1k?.
Using these values, calculate the current gain Ai.
Q1(d)
[7 Marks]
For the circuit of Fig Q1(b), derive an expression for the voltage gain Av = Vce/Vbe.
Q1(e)
[2 Marks]
Assuming the circuit has the same values as described by Q1(c) above, calculate the voltage
gain Av for this circuit.
Q1(f)
[5 Marks]
For the CE circuit of FigQ1(b) above, derive an expression for the input impedance Zin and
hence calculate its value based on the values described in Q1(c) above.

Added by Alexander S.

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