ABSTRACT
Common use for analog switches and multiplexer is passive component selection. Because analog switches are bidirectional, they may be used with resistors, capacitors, and inductors to connect or isolate them from the rest of the circuit. They may also be placed in parallel with these devices to short past them. This allows the user to have digital control over passive component values. Digital-to-analog converters (DAC) often use resistive ladders controlled by analog switches. The R-2R ladder is a more cost-effective way to achieve higher resolution DACs without using thousands of resistors. The R-2R ladder is different from the simple ladder in that while the simple ladder is a voltage divider, the R-2R ladder converts the input voltage into an output current. Programmable filters, oscillators and integrators are frequently made with analog switches. The analog switches select which resistors and/or capacitors are connected, placing the system time constants under digital control.
