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प्रश्न
Find the values of rp, µ and gm of a triode operating at plate voltage 200 V and grid voltage −6. The plate characteristics are shown in the figure.
उत्तर
Dynamic plate resistance, `r_p=((deltaV_p)/(deltaI_p)),` at constant grid voltage
We need to find the slope of the graph for a particular value of grid voltage, i.e. Vg = −6 V.
Consider two points for the plot of Vg = −6 V:-
\[r_p = \frac{(240 - 160) V}{(13 - 3) \times {10}^{- 3} A}\]
\[ r_p = \frac{80}{10} \times {10}^3 \Omega\]
\[ r_p = 8 K\Omega\]
\[ g_m = \left( \frac{\delta I_p}{\delta V_g} \right)_{V_P = \text{constant } (200 V)}\]
Consider two points on the 200 V line:-
\[g_m = \frac{(13 - 3) \times {10}^{- 3}}{[( - 4) - ( - 8)]}A\]
\[ g_m = \frac{10 \times {10}^{- 3}}{4}=2.5\text{ mili mho}\]
Amplification factor,
\[\mu = - \left( \frac{∆ V_P}{∆ V_G} \right)_{i_P =\text{ constant}}\]
\[\mu = - \frac{100 - 180}{- 6 - ( - 10)}\]
\[\mu = \frac{80}{4} = 20\]
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