Question

The relation between amplification factor $ (\mu ), $ plate resistance $ ({{r}_{p}}) $ and mutual conductance $ ({{g}_{m}}) $ of a triode valve is given by

• A. $ \mu ={{r}_{p}}\times {{g}_{m}} $
• B. $ {{r}_{p}}=\mu \times {{g}_{m}} $
• C. $ {{g}_{m}}=\mu \times {{r}_{p}} $
• D. none of these

Answer 1

Answer: (A)

The amplification factor $(\mu)$ is given by
$\mu=\left(\frac{\Delta V_{p}}{\Delta V_{g}}\right)_{I_{p}=\text { constant }}\ldots$(i)
Plate resistance
$r_{p}=\left(\frac{\Delta V_{p}}{\Delta I_{g}}\right)_{V_{g}=\text { constant }}\ldots$(ii)
Transconductance
$g_{m} =\left(\frac{\Delta I_{p}}{\Delta V_{g}}\right)_{v_{p}=\text { constant }} \ldots$(iii)
$\therefore \mu =\frac{\Delta V_{p}}{\Delta V_{g}}=\frac{\Delta V_{p}}{\Delta I_{p}} \times \frac{\Delta I_{p}}{\Delta V_{g}}$
From Eqs. (ii) and (iii), we get
$\mu=r_{p} \times g_{m}$