R5620 ... a programmable universal filter with switched capacitors

R5620 ... a programmable universal filter with switched capacitors As their name implies, switched capacitor filters (SCFs) make use of switched capacitors as adjustable components, instead of variable resistors. Th is technique allows filter circuits to be completely integrated, with the filter parameters remaining extensively variable. The special feature is that SCFs require almost no external components. The centre frequency (fo), for example has a fixed relationship with the clock frequency (ft). Varying ft results in an automatic variation of f o. Particu- lar, fixed frequency ratios between filters can therefore be achieved with ease and precision, by inserting flip-flops and similar digital circuits into the clock frequency line. We shall not go into more theory at this stage; those readers interested in obtaining further details can consult the literature referred to in this article. Programmable and universal If the R 5620 were only an improved version of its predecessor...