switched capacitors - up-to-date filters in a single IC

10-12 — elektor october 1980 switched capacitors On one side there is a voltage ui, on the other a voltage u2. For simplicity"s sake it will be assumed that u1is greater than u2. Then a current i will pass through resistor R from left to right. According to Ohm"s Law: 1-11 — u2 R— Back and forth Figure 1b constitutes the "imitation resistor". Switch S continually switches back and forth between u1and u2. The frequency at which that happens is called f. Whenever S is in position a the capacitor C is charged to the voltage level u1. Whenever it is in position b it is discharged to the level of u 2 (still assuming u1to be greater than u2). This enables a charge to be trans- ferred from u1to u2, which is exactly what a resistor does, only a resistor is Signals are filtered in every possible branch and application of electronics. In every case certain signals have to be selected for a special purpose: for instance, radio and television broad- cats depend on the ability to single ...