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Question: A triode has a mutual conductance of \(2 \times 10^{- 3}mho\) and an amplification factor of 50. The...

A triode has a mutual conductance of 2×103mho2 \times 10^{- 3}mho and an amplification factor of 50. The anode is connected through a resistance of 25×10325 \times 10^{3} ohms to a 250 volts supply. The voltage gain of this amplifier is

A

50

B

25

C

100

D

12.5

Answer

25

Explanation

Solution

Using AV=μ1+rpRLA_{V} = \frac{\mu}{1 + \frac{r_{p}}{R_{L}}}and μ=rp×gm\mu = r_{p} \times g_{m}

rp=μgm=502×103=25×103Ω\Rightarrow r_{p} = \frac{\mu}{g_{m}} = \frac{50}{2 \times 10^{- 3}} = 25 \times 10^{3}\Omega

Av=501+25×10325×103=25.\therefore A_{v} = \frac{50}{1 + \frac{25 \times 10^{3}}{25 \times 10^{3}}} = 25.