
Switched-Capacitor Filters
111
Note that the smallest feedback factor is equal to 0.665. From Equation (4.30),
we can thus fi nd that w
ol
should not be smaller than 842.11 Mrad/s, or, equivalently,
134.026 MHz. For the sake of design margin, we specify that each op-amp in the
fi lter have a UGBW of no less than 140 MHz.
The third important op-amp parameter to be determined is the slew rate. Slew
rate is known as the rate at which the output changes when the input signal has large
steps. The slew rate of an op-amp can also be defi ned as the rate at which the op-amp
is able to charge or discharge the capacitive load (C
L
) at its output terminal [1