Environmental Engineering Reference
In-Depth Information
compensation technique is a variant of the nested-Miller one and is called
hybrid nested Miller. We shall not discuss this technique here, for details
interested readers are referred to [EH95].
6.6.4 Frequency Compensation of the Series-Series Amplifier
Drawing the high-frequency small-signal circuit of the series-series
amplifier in Fig. 6.24 is left to the reader.
For the series-series amplifier, the circuit path for evaluating the return
ratio includes the gain stage provided by transistor T2, transistor T3 (which
acts as a voltage buffer), the feedback resistors, and transistor T1 which acts
as a current follower. Again, the load impedance is outside the loop, and
hence does not play any role in the compensation process. Given the
presence of an inverting gain stage with both input/output high-resistance
terminals, Miller compensation is the most suitable technique.
Thus, transconductance of the equivalent model in Fig. 6.31 must be
assumed to be the equivalent transconductance
of transistor T2
and resistors
and
are given by
In (6.90) the loading effect of the feedback network can be neglected
because of the buffering operation of transistor T1.
Finally, assuming T1 and T3 to be ideal current and voltage follower,
respectively, we get
