Environmental Engineering Reference
In-Depth Information
increase in capacitance
at the high-resistance node, Z. In order to provide
a given phase margin,
the relationship
holds, where
is the equivalent second pole generally due to load
capacitance
[P99]
Even if there is no load capacitor outside the chip, there is a contribution
internal to the IC caused by the bounding pad and pin capacitances.
Other frequency limitations are due to the transfer functions and
h
(s) characterised by high-frequency poles given that they arise at low
resistance nodes. They can therefore be neglected in a first-order analysis.
Observe, however, that those poles associated with the output voltage buffer
transfer function are much higher than those of the current mirrors.
In conclusion, using (9.26), with
set to zero, in relationship (9.27) we
get
9.6 INTEGRATORS AND DIFFERENTIATORS WITH CFOAs
As a useful application we shall now consider the implementation of a
simple integrator and differentiator using the CFOA. These circuits are
shown in Figs. 9.16 and 9.17, respectively.
