Active-R Bandpass Filter Design Using Hybrid-Pi Transistor Model.

A design procedure is developed for a bandpass filter utilizing five bipolar transistors and no external capacitors. Base resistors of a three-stage amplifier are used to set a third-order open-loop pole at a location given in terms of the center frequency and bandwidth of the filter. A feedback resistor, also given in terms of the center frequency and bandwidth, is then used to move the poles to the final location. A test circuit is constructed and compared with a computer simulation. Limitations of the circuit are discussed. Author