Environmental Engineering Reference
In-Depth Information
Transistor T3, highly reduces the open-loop output resistance,
which becomes quite independent of feedback resistance, The foregoing
improvement can be confirmed through an analysis of the small-signal
model of the modified amplifier in Fig. 6.9. To this end, assume transistor
T3 a quite ideal voltage follower with unitary gain and with an input
resistance much higher than resistance The loop gain of the circuit in
Fig. 6.9 can be evaluated by using the small signal model in Fig 6.10, which
can be further simplified by using a Norton equivalent current generator.
After some approximations the ultimate circuit model is that shown in Fig.
6.11.
Consequently, (6.6) can now be rewritten as
