Environmental Engineering Reference
In-Depth Information
Equation (5.45), in addition to a dominant pole, also includes two other
higher poles and two zeros. Moreover, since the coefficients of the
s
and
terms in the numerator are both negative, a RHP zero is created, which is
located at a lower frequency than the other LHP zero. In analogy to the
discussion of the previous paragraph, using voltage followers or current
followers can nominally eliminate both zeros. Another solution is the
multipath
Miller approach proposed in [YES97] that, according to Fig. 5.8,
provides a zero cancellation due to the effect described in [EH95]. In brief,
the forward path contribution is ideally nullified by setting
equal to
When using any of these techniques, or in the case of a very large
such as in power amplifiers (whose output stage is biased with large
quiescent currents and is realised with large devices), relationship (5.45)
simplifies to
