Environmental Engineering Reference
In-Depth Information
It is worth noting that the input voltage buffer is outside the feedback
loop and hence does not affect the frequency response and stability of the
amplifier. The feedback loop of the amplifier includes the output voltage
buffer (T9-T12), resistances and transistors T3 and T4, which work as
simple common-base amplifiers, and the two current mirrors T5-T6 and T7-
T8.
A simple small-signal model of the CFOA is shown in Fig. 9.14 where
is the equivalent resistance at gain node Z. The output resistance of the input
voltage buffer, is the input resistance at inverting node, and the input
resistance of the input buffer, is the input resistance of the noninverting
node. The output resistance of the output voltage buffer, is the output
resistance. Controlled generators and
h
model the transfer functions
of the input and output voltage buffer, and the complementary current
mirror, respectively, and are usually almost unitary in module.
By inspection of Fig. 9.13, we get
