Programming instructions

Vacuum Tube
 National Instruments Corporation 13-5 Multisim Component Reference Guide
13.4 Vacuum Tube
This component behaves as a three-electrode tube consisting of an anode, cathode and plate
electrode. It is often used as an amplifier in audio applications.
The vacuum tube is a voltage controlled current device, very similar in operation to an N
channel FET.
As for an FET, the gain of the tube is referred to as transconductance and is defined as the
change in plate current resulting from a change in grid to cathode voltage:
gm = (change in plate current) / (change in grid to cathode voltage)
13.4.1 Characteristic Equations
The DC characteristic of the triode vacuum tube is modeled by a two-dimensional voltage-
controlled current:
where
Other items are defined in “Triode Vacuum Tube Parameters and Defaults”.
()
I
KVV
p
gk pk
=
∗+ ∗ + ≥
∗+ <





µµ
µ
3
2
V V 0
0 V V 0
for
for
gk pk
gk pk
()
K
I
VV
p
gk pk
=
∗+
µ
3
2
ComponentRef.book Page 5 Thursday, December 7, 2006 10:12 AM