Page 122 - Op Amps Design, Applications, and Troubleshooting
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AC-Coupled Amplifier 105
1
A similar computation, Equation (2.41), for the output RC circuit is
Computing the ratio of the two cutoff frequencies (using the higher frequency
as the numerator) gives us the index needed for the lookup operation in Table 2.5.
For our particular case, the index is computed as
Finally, we use the lookup table shown in Table 2.5 to get our multiplyinj
factor k. In this case, the value of k is about 1.32 (estimating the value between 13
and 1.306). The overall lower cutoff frequency can now be found by multiplyin;
our factor k by the higher of the two individual cutoff frequencies.
Thus, the lower cutoff frequency for the circuit in Figure 2.27(a) is estimated as
The approximate bandwidth of the circuit in Figure 2.27(a) can now be expressed
as Equation (2.5):
