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
$\mu ={\left(\frac{\Delta V_p}{\Delta V_g}\right)}_{I_p=\text{ constant }}\dots$(i)
Plate resistance
$r_p={\left(\frac{\Delta V_p}{\Delta I_g}\right)}_{V_g=\text{ constant }}\dots$(ii)
Transconductance
$g_m={\left(\frac{\Delta I_p}{\Delta V_g}\right)}_{v_p=\text{ constant }}\dots$(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
$\mu =r_p\times g_m$