Q. 16

# Find the values of r_{p}, μ and g_{m} of a triode operating at plate voltage 200 V and grid voltage –6 V. The plate characteristics are shown in figure.

Answer :

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

From figure, considering the line V_{g}=-6 V, we get two value of V_{P} i.e.

V_{P1}=160 V , V_{P2}=240 V , Also i_{p1}=3 mA i_{p2}=13mA

Substituting values in equation we get,

The mutual inductance g_{m} of a triode valve is defined as

Considering two points in the graph where V_{p=}200 V we get i_{p1}=13 mA i_{p2}=3mA V_{g1}=-4 V, V_{g2}=-8 V

Substituting values in equation we get.

Rate this question :

A triode has mutual conductance = 2.0 millimho and plate resistance = 20 kΩ. It is desired to amplify a signal by a factor of 30. What load resistance should be added in the circuit?

HC Verma - Concepts of Physics Part 2Find the values of r_{p}, μ and g_{m} of a triode operating at plate voltage 200 V and grid voltage –6 V. The plate characteristics are shown in figure.

HC Verma - Concepts of Physics Part 2

The plate current in a triode can be written as

Show that the mutual conductance is proportional to the cube root of the plate current.

HC Verma - Concepts of Physics Part 2

The gain factor of an amplifier is increased from 10 to 12 as the load resistance is changed from 4 kΩ to 8 KΩ. Calculate (a) the amplification factor and (b) the plate resistance.

HC Verma - Concepts of Physics Part 2The plate current in a diode is 20 mA when the plate voltage is 50 V or 60 V. What will be the current if the plate voltage is 70V?

HC Verma - Concepts of Physics Part 2