Environmental Engineering Reference
In-Depth Information
CFOAs have become popular because of their inherent advantages:
excellent small-signal and large signal performance and, under proper
operating conditions, a closed-loop bandwidth independent of gain. In fact,
thanks to the low-impedance input terminal, the typical closed-loop
bandwidth is in the range of 50 to 100 MHz and a very high slew rate
capability in the range of 500- to [B90], [S911], [SS92], [G93],
[B93], [SKW94], [B97] has been reported. The high slew rate performance
derives from the use of a class AB topology for both the input and output
stages. Although the differential stages with class AB capability, reported in
the literature [SW87], [BW83], [C93], [CMPP93], could be used in
conventional opamps to provide a high slew-rate, this option is rather
unusual and expensive.
The closed-loop constant-bandwidth property offered by a CFOA can be
easily explained by considering the closed-loop configuration shown in Fig.
9.12.
The asymptotic gain and the loop gain of the circuit can be found using
the Rosentark method, choosing the dependent output voltage generator as
