Transconductance

It is defined as follows: For small signal alternating current, the definition is simpler: The SI unit for transconductance is the siemens, with the symbol S, as in conductance.

It is one of the three characteristic constants of a vacuum tube, the other two being its gain μ (mu) and plate resistance rp or ra.

15, §0127 Additionally, the transconductance for the junction FET is given by where VP is the pinchoff voltage, and IDSS is the maximum drain current.

The gm of bipolar small-signal transistors varies widely, being proportional to the collector current.

The transconductance for the bipolar transistor can be expressed as where IC is the DC collector current at the Q-point, and VT is the thermal voltage, typically about 26 mV at room temperature.

In network analysis, the transconductance amplifier is defined as a voltage controlled current source (VCCS).

The term for a transresistance amplifier in network analysis is current controlled voltage source (CCVS).