Question

The amplification factor of a triode is 20 and trans-conductance is 3 milli mho and load resistance 3 × 10⁴ Ω, then the voltage gain is
1. 16.36
2. 28
3. 78
4. 108

Answer 1

Correct Answer - Option 1 : 16.36

Using voltage gain \({A_v} = \frac{\mu }{{1 + \frac{{{r_p}}}{{{R_L}}}}}\)

Also Amplification factor, μ = r_p × g_m

\(\Rightarrow Plate\;resistance,\;{r_p} = \frac{\mu }{{{g_m}}} = \frac{{20}}{{3 \times {{10}^{ - 3}}}}\)

\(\therefore {A_v} = \frac{{20}}{{1 + \frac{{20}}{{3 \times {{10}^{ - 3}} \times 3 \times {{10}^4}}}}} = \frac{{20}}{{1 + \frac{{20}}{{3 \times {{10}^{ - 3}} \times 3 \times {{10}^4}}}}} = \frac{{20}}{{1 + \frac{2}{9}}} = \frac{{180}}{{11}} = 16.36\)