The TLVx365 is an excellent choice for active filter applications requiring a wide bandwidth, fast slew rate, low-noise, single-supply operational amplifier. Figure 8-6 shows a 500-kHz, second-order, low-pass filter using a multiple-feedback (MFB) topology. The components have been selected to provide a maximally-flat Butterworth response. Beyond the cutoff frequency, rolloff is −40 dB/dec. The Butterworth response is designed for applications requiring predictable gain characteristics, such as the antialiasing filter used ahead of an ADC.

Figure 8-6 Second-Order Butterworth, 500-kHz Low-Pass Filter

When considering the MFB filter, the output is inverted, relative to the input. If this inversion is not desired, then a noninverting output can be achieved through one of these options:

• add an inverting amplifier
• add an additional second-order MFB stage
• use a noninverting filter topology, such as the Sallen-Key

Figure 8-7 shows the Sallen-Key topology.

Figure 8-7 Configured as a Three-Pole, 20-kHz, Sallen-Key Filter