Low-power, low-noise, active-RC band-pass filters using a 'lossy' LP-BP transformation

SUMMARY A new and straightforward design procedure for simple canonical topologies of allpole, active‐RC, low‐selectivity band‐pass (BP) filters, with low sensitivity to component tolerances is presented. The procedure is primarily intended for discrete‐component, low‐power filter applications using just one amplifier for relatively high‐order filters. The design procedure starts out with an ‘optimized’ low‐pass (LP) prototype filter, yielding an ‘optimized’ BP filter, whereby the wealth of ‘optimized’ single‐amplifier LP filter designs can be exploited. Using a so‐called ‘lossy’ LP–BP transformation, closed‐form design equations for the design of second‐ to eighth‐order, single‐amplifier BP filters are presented. The low sensitivity, low power consumption, and low noise features of the resulting circuits, as well as the influence of the finite gain‐bandwidth product and component spread, are demonstrated for the case of a fourth‐order filter example. The optimized single‐opamp fourth‐order filter is compared with other designs, such as the cascade of optimized Biquads. Using PSpice with a TL081 opamp model, the filter performance is simulated and the results compared and verified with measurements of a discrete‐component breadboard filter using 1% resistors, 1% capacitors, and a TL081 opamp. Copyright © 2011 John Wiley & Sons, Ltd. A new design procedure for single‐opamp low‐power, discrete‐component, lowselectivity, low‐sensitivity and low‐noise active‐RC band‐pass filters. Considering all performance characteristics the advantages of the new design technique outweigh those of other design techniques, for example cascade of Biquads. Using a so‐called ‘lossy’ LP‐BP transformation, closed‐form design equations for the design of secondto eighth‐order, single‐amplifier BP filters are presented. Copyright © 2011 John Wiley & Sons, Ltd.