Transconductance Amplifier – Definition and Equivalent Circuit:

In transconductance amplifiers the input signal is a voltage and its output signal is a current. The ideal transconductance amplifier provides an output current which is proportional to the signal voltage and the proportionality constant is independent of the magnitudes of R_s and R_L.

From the equivalent circuit of a transconductance amplifier depicted in Fig. 19.4, we find that if R_s << R_in, then V_in ≈ V_s and if load resistance R_L << R_out,

then

and

An ideal transconductance amplifier should have infinite input and output resistances.