4.4.3 Alternative Third-Order Component Computation

It is also possible to add the first-order cell at the output of the operational amplifier, like the second one in the fourth-order low-pass filter described in Flexible Fourth-Order Component Computation.

The main advantage of this alternative configuration is that the first-order cell no longer interferes with the second-order cell computation. The drawback is the penalty on gain, as the loss cannot be compensated by the amplifier gain. Computation is straightforward using the “Second Order” Excel spreadsheet.