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)

$\mu ={{r}_{p}}\times {{g}_{m}}$

Answer 2

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 $\mu=r_{p} \times g_{m}$