CHAPTER 15: ACTIVE FILTER CIRCUITS
1 Contents
15.1 First-Order Low-Pass and High-Pass Filters
15.2 Scaling
15.3 Op Amp Bandpass and Bandreject Filters
15.4 High Order Op Amp Filters
15.5 Narrowband Bandpass and Bandreject Filters
Electronic Circuits, Tenth Edition J ames W. Nilsson | Susan A. Riedel 2 15.1 1st-Order Low-Pass and High-Pass Filters
• Active filters consist of op amps, resistors, and capacitors. • They overcome many of the disadvantages associated with passive filters.
A first-order low-pass filter.
A first-order low-pass filter. A general op amp circuit.
• At very low frequencies, the capacitor acts like an open circuit, and the op amp circuit acts like an amplifier with a gain. • At very high frequencies, the capacitor acts like a short circuit, thereby connecting the output of the op amp circuit to ground.
Electronic Circuits, Tenth Edition J ames W. Nilsson | Susan A. Riedel 3 15.1 1st-Order Low-Pass and High-Pass Filters
Transfer function for the circuit