Question

Find the values of rp, µ and gm of a triode operating at plate voltage 200 V and grid voltage −6. The plate characteristics are shown in the figure.
Figure

Answer 1

The values of rp, µ and gm is 8 KΩgm, 20 and 2.5 mili mho, respectively.

EXPLANATION:

• Resistance of dynamic plate,

• At the constant grid voltage, rp = δVpδIp

• The slope of the graph needs to be found for a particular value of grid voltage, i.e. Vg = −6 V.

• For the plot, consider two points, Vg = −6 V:

• rp = (240-160) V(13-3) × 10-3 Arp = 8010 × 103 Ωrp = 8 KΩgm = constant (200 V)

• On the 200 V line, consider two points:

• gm = (13-3) × 10-3[(-4)-(-8)]Agm = 2.5 mili mho

• Amplification factor,
• μ = 20