1.
The Constants of the Triode:
1.
Amplification Factor: It is the ratio of the change in
plate voltage to the change in grid voltage for a constant plate current.
m =

dV_{p}



I_{p}
= constant. The amplification factor m has no unit.


dV_{g}

2.
3.
Transconductance: It is the ratio of
the change in plate current to the change in grid voltage for a constant
plate voltage.
gm =

dI_{p}



V_{p}
= constant. The unit of transconductance gm is
mho or siemens.


dV_{g}

4.
5.
Plate Resistance: It is the ratio of change in plate voltage
to the change in plate current when the grid voltage is kept constant.
r_{p} =

dV_{p}



V_{g} = constant.


di_{p}

2.
3.
Relation between Triode Constants: m = r_{p} × g_{m}.
4.
The 'ChildLangmuir Law': In the space charge
region of the vacuum diode characteristic, the relation between the plate
current (I_{p})
and the plate potential (V_{p})
is given approximately by the 'ChildLangmuir Law'
which is as follows:
I_{p} = KV_{p}^{3/2},
where

I_{p}

= plate current


K

= constant


V_{p}

= plate potential

5.

Vacuum diode
characteristic


6.
