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Question: With a change of load resistance of a triode, used as an amplifier, from 50 kilo ohms to 100 kilo oh...

With a change of load resistance of a triode, used as an amplifier, from 50 kilo ohms to 100 kilo ohms, its voltage amplification changes from 25 to 30. Plate resistance of the triode is.

A

25 kΩ

B

75 kΩ

C

7.5 kΩ

D

2.5 kΩ

Answer

25 kΩ

Explanation

Solution

Voltage amplification Av=μ1+rpRLA_{v} = \frac{\mu}{1 + \frac{r_{p}}{R_{L}}}

25=μ1+rp50×103\Rightarrow 25 = \frac{\mu}{1 + \frac{r_{p}}{50 \times 10^{3}}} ......(i)

And 30=μ1+rp100×10330 = \frac{\mu}{1 + \frac{r_{p}}{100 \times 10^{3}}} ......(ii)

an solving equation (i) and (ii), rp=25kΩ.r_{p} = 25k\Omega.