Electronic Devices Question 253
Question: The linear portions of the characteristic curves of a triode valve give the following readings $ V _{g} $ (volt) 0 ? 2 ? 4 ? 6
$ I _{p}(mA) $ for $ V _{p}=150 $ volts 15 12.5 10 7.5 $ I _{p}(mA) $ for $ V _{p}=120 $ volts 10 7.5 5 2.5 The plate resistance is
[Roorkee 1985]
Options:
A) 2000 ohms
B) 4000 ohms
C) 8000 ohms
D) 6000 ohms
Show Answer
Answer:
Correct Answer: D
Solution:
$ g _{m}=( \frac{\Delta i_p}{\Delta V_g} ) _{V _{p}=\text{constant}}$=
$\frac{(15-10)\times {{10}^{-3}}}{0-(-4)}=1.25\times {{10}^{-3}}\Omega $
$ \mu ={{( \frac{\Delta V _{p}}{\Delta V _{g}} )} _{I _{p}=\text{constant}}}$=
$\frac{150-120}{0-(-4)}=7.5 $
$ r _{p}=\frac{\mu }{g _{m}}=\frac{7.5}{1.25\times {{10}^{-3}}}=6000 $ ohms
