Environmental Engineering Reference
In-Depth Information
by transistor T3, we get the same return ratio as the series-shunt feedback
amplifier with output buffer in Fig. 6.9. Hence, it is about equal to (6.27)
Consider the transconductance infinitely large. Since the voltage is
still finite, the voltage must be zero. This implies that the current
provided by terminal Z of transistor Tl must be zero, and hence the voltage
and the associated current given by the voltage source must be zero. In
conclusion, the asymptotic transconductance can be evaluated on the
equivalent AC model in Fig. 6.25.
In particular, the voltage at terminal X of transistor T1 (node X1 in Fig.
6.25) is equal to the source voltage. Furthermore, transistor T1 does not
supply current. The current through resistance (i.e.,
is thus
equal to that flowing through resistance
Besides, the voltage on node X3,
which defines the current of resistance
is
and the current which flows into node X3 is equal to
