The plate resistance and the amplification factor of a triode are 10 kΩ and 20. The tube is operated at plate voltage 250 V and grid voltage –7.5 V. The plate current is 10 mA (a) To what value should the grid voltage be changed so as to increase the plate current to 15 mA? (b) To what value should the plate voltage be changed to take the plate current back to 10 mA?

Question

Philoid · Accepted Answer

Given, r_p=10kΩ, μ=20, V_P1=250 V. Vg₁=-7.5 V, ip₁=10 mA

a) CASE 1: i_p2=15 mA. V_P= Constant, Vg₂=? i_p1=10 mA

We know,

where r_p is the plate resistance and g_m is the trans-conductance

mho

Now,

where ΔV_g is the change in grid voltage and V_p is the plate voltage and ΔI_p is the change in plate current

b)CASE 2: V_P3=?,i_p3=10 mA, i_p2=15mA, i_p3=10mA

The dynamic resistance of triode is defined as,

where ΔV_p is the change in plate voltage and V_g is the grid voltage and ΔI_p is the change in plate current

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V, required voltage