digitally tunable capacitor (DTC)
In the case of capacitors, a distinction is made between the various fixed capacitors and those with tunable capacitance. The latter include variable capacitors, trimmers, capacitance diodes and digitally tunable capacitors (DTC).
Digitally Tunable Capacitors are variable capacitors built in chip form using CMOS or UltraCMOS technology. DCT capacitors consist of several MOS capacitors that are switched on or off via MOSFETs. For example, with five capacitors, a total of 32 different capacitance values can be added to the existing capacitance. If the base capacitance of a DTC capacitor is 10 pF and the five capacitors have capacitances of 1 pF, 2 pF, 4 pF, 8 pF and 16 pF, then the tuning ratio is 10 pF to 41 pF, or 1:4.1. By switching them on and off, any value between 10 pF and 41 pF can be selected. Since DTC capacitors use MOSFET switches, they have a high Q factor, which can be 100 or more.
DTC capacitors are used in RF oscillators, in digitally tunable RF filters, and in smartphone antennas for standing wave ratio( VSWR) adjustment and reconfigurable antennas, among other applications.