Question

A triode value operates at V_p = 225 V and V_g = −0.5 V.
The plate current remains unchanged if the plate voltage is increased to 250 V and the grid voltage is decreased to −2.5 V. Calculate the amplification factor.

Answer 1

Amplification factor for a triode valve,
$\mu =\frac{\mathrm{Change}\mathrm{in}\mathrm{Plate}\mathrm{Voltage}}{\mathrm{Change}\mathrm{in}\mathrm{Grid}\mathrm{Voltage}}$
At constant plate current,
$$\begin{gathered} \mu =(\frac{\delta V_{\mathrm{P}}}{\delta V_{\mathrm{G}}}{)}_{i_P=\mathrm{constant}} \\ \mu =\frac{250-225}{2.5-0.5} \\ \mu =\frac{25}{2}=12.5 \end{gathered}$$

This implies that the amplification factor of the triode is 12.5 .