Editing Transconductance (section)

=== Vacuum tubes ===
For [[vacuum tube]]s, transconductance is defined as the change in the plate (anode) current divided by the corresponding change in the grid/cathode voltage, with a constant plate (anode) to cathode voltage. Typical values of {{math|''g''<sub>m</sub>}} for a small-signal vacuum tube are 1 to {{val|10|u=mS}}. It is one of the three characteristic constants of a vacuum tube, the other two being its [[Gain (electronics)|gain]] {{mvar|μ}} (mu) and plate resistance {{math|''r''<sub>p</sub>}} or {{math|''r''<sub>a</sub>}}. The [[Hendrik van der Bijl|Van der Bijl]] equation defines their relation as follows:
: <math>g_\mathrm{m} = \frac{\mu}{r_\mathrm{p}}</math><ref>Blencowe, Merlin (2009). "Designing Tube Amplifiers for Guitar and Bass".</ref>