Varicap

(redirected from Varicap diode)

varicap

[′var·ə‚kap]
(electronics)

Varicap

 

a condenser in the form of a semiconductor diode whose capacitance depends nonlinearly on the voltage applied to it. This capacitance is the barrier capacity of the p-n junction; it varies from a few to hundreds of picofarads (in certain variable-capacitance diodes, virtually by a factor of 3-4) in case of variations of several dozen volts in the reverse (negative-sign) current. Varicaps have high efficiency (minor losses of electrical energy) and a low temperature coefficient of capacitance, independence of frequency in virtually the entire range of radio frequencies, and stability of parameters with time. Varicaps are manufactured from silicon, germanium, and gallium arsenide. In radio and electronic equipment, the characteristic of nonlinear variation of capacitance in varicaps is used to obtain parametric amplification and frequency multiplication, and the possibility of electrical control of the capacitance value is used for remote and noninertial tuning of the resonance frequency of oscillatory circuits.

REFERENCES

Berman, L. S. Nelineinaia poluprovodnikovaia emkost’. Moscow, 1963.
Berman, L. S. Vvedenie v fiziku varikapov. Leningrad, 1968. (Bibliography, pp. 174-78.)
Labutin, V. K. Chastotno-izbiratel’nye tsepi s elektronnoi nastroikoi. Moscow-Leningrad, 1966.
References in periodicals archive ?
In [19] and [20], the performances of the BST capacitor are compared to the ones of the varicap diode. These results showed that the BST capacitor has better linearity of the variation frequency with respect to control voltage and also better signal spectral purity.
The design of the active frequency stabilization oscillator and the initial experimental verification started from the hypothesis according to which the performances of an oscillator can be significantly enhanced by replacing the varicap diode with a BST capacitor.
The next set of measurements was performed after replacing the control frequency varicap diode, with a 6.8pF controllable BST capacitor, commercially referred to as STPTIC.
6, the oscillator frequency has a very good stability, significantly better compared to the one of the original oscillator with varicap diode and a 26 MHz quartz crystal.
The first experimental results were obtained using an industrial TCXO oscillator and were aimed to confirm the hypothesis according to which a BST capacitor can provide significantly enhanced performances compared to a varicap diode. Thus, these initial results have showed that the usage of the BST capacitor provided better frequency stability and also a wide frequency control range.
Figure 5 shows the integration of a low band filter prior to the varicap diode of the oscillator using temperature-stabilized components.
The high side voltage-controlled LO uses an external varicap diode and tank resonator circuit that produce a first IF of 70 MHz.
Varicap diodes (or varactors) are also a type of RF filter that is often utilized as voltage-controlled capacitors and is incorporated in TV tuners to electronically tune the receiver to different stations.
announced two tunable antenna varicap diodes for digital terrestrial broadcast capable portable and mobile terminals, the RKV653KP featuring industry's smallest size of 0.6mm x 0.3 mm and the extended-package RKV653KL.
Table 1 lists the typical characteristics of these new varicap diodes.