Varicaps, varactors or variable-capacitance diodes are semiconductor devices whose capacitance depends on the reverse bias voltage. These components are used in tuned circuits to change the frequency from an external control voltage.
Formula 1
Varicap:
Where:
Cd is the final capacitance in picofarads (pF)
Co is the capacitance when U = 0 V
n is the index given by the manufacturer according the device
V is the applied voltage in volts (V)
Vo is the diffusion voltage in volts (V)
Note: Vo = 0.5 V(typ) for germanium
Vo = 0.7 V(typ) for silicon
