Question 141: Semiconductors and Logic Gates

Question

An NPN transistor is used in common emitter
configuration as an amplifier with 1 k$$\Omega $$ load
resistance. Signal voltage of 10 mV is applied
across the base-emitter. This produces a 3 mA
change in the collector current and 15μA
change in the base current of the amplifier. The
input resistance and voltage gain are :

Accepted Answer

Input current = 15 ÃÂ 10
Ã¢ÂÂ6
Output current = 3 ÃÂ 10
Ã¢ÂÂ3
Resistance out put = 1000
V
input
= 10 ÃÂ 10
Ã¢ÂÂ3
Now V
input
= r
input
ÃÂ i
input
10 ÃÂ 10
Ã¢ÂÂ3
= r
input
ÃÂ 15 ÃÂ 10
Ã¢ÂÂ6
r
input
= $${{2000} \over 3} = 0.67\,K\Omega $$
Voltage gain = $${{{V_{output}}} \over {{V_{input}}}} = {{1000 	imes 3 	imes {{10}^{ - 3}}} \over {10 	imes {{10}^{ - 3}}}} = 300$$

Answer

0.67 kW, 200

Answer

0.33 kW, 1.5

Answer

0.67 kW, 300

Answer

0.33 kW, 300

Semiconductors and Logic Gates

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