The plate resistance of a triode is `8 kOmega` and the transconductiance is `2.5 millimho. (a) If the plate voltage is increased by `48 V`, and the grid voltage is kept constant, what will be the increase in the plate current? (b) With plate voltage kept constant at this increased value, how much should the grid voltage be decreased in order to bring the plate current back to its initial value?

Explanation

(a) We have
` r_p = 8KW = 8000 W `
` omega V_p = 48V omega I_p = ? `
` omega I_p = omega V_p/r_p [V_p rarr Constant ]`
` So, omega I_p = 48/8000 = 0.006A = 6mA.`
` (b) Now, V_p is constant `
` omega I_p = 6 Ina = 0.006A, `
` g_m = 0.0025mho `
omegav_g = (omegaI_p/g_m) = 0.006/0.0025`
` = 2.4V [V_p rarr Constant] ` .