Bias Circuit

RG can be selected somewhat arbitrarily but could be dictated by the coupling capacitor, CG,
requirement. Associated with the coupling capacitor is the 3 - dB frequency (6.2), which is
RG2 is then calculated from
The gain equations for the circuit of Fig. 5.9, with and without a bypass capacitor, are (5.2)
and (5.15), respectively. These are
av = –gmRD
and
In the design procedure outlined in this unit, emphasis is on stability and the gain falls out.
This would typically be the case for this type of amplifier. We note that due to the
characteristically small gm of MOSFETs, the voltage gain is relatively small. Gain can be
improved considerably through the use a current-source load, as in the amplifier of Unit 10.