**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.