Environmental Engineering Reference
In-Depth Information
To simplify calculation, assume that is much higher than and
and that is the lower resistance at node Y of transistor T2. Using
equation (2.38c), expressing the voltage gain of a common Z transistor, the
loop gain results to be
which, neglecting the voltage loss between terminals Y and X of T2, lastly
simplifies to
3)
Now we evaluate the closed loop asymptotic gain. By inspection of
Fig. 6.13, we realise that setting the parameter infinitely large leads
to equal zero, which in turn means that all the input current, flows into
feedback resistance, In addition, since a finite value of current
would cause to be different from zero, term itself must equal
zero. With these considerations, we can model the circuit with that in Fig.
6.18.
