Varactor diode
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Varactor diode is a type of PN junction diode where the capacitance of the PN junction can be controlled by applying a reverse bias voltage. As the reverse bias voltage is changed, the width of the depletion region between the P and N semiconductors changes, altering the capacitance. Varactor diodes are commonly used in applications like variable resonant tank circuits, automatic frequency control circuits, and frequency modulation in radios and televisions. They operate by varying the capacitance through adjustment of the depletion region width, similar to how the distance between capacitor plates controls capacitance.
Varactor diode
- 1. VARACTOR DIODE Nyamador Enock Seth University of Mines and Technology (UMaT), Tarkwa Computer Science and Engineering ‘14 Twitter: @enock4seth
- 2. INTRODUCTION Varactor diode is a special type of PN junction diode, in which PN junction capacitance is controlled using reverse bias voltage. When the diode is forward biased, current will flow through the diode. When the diode is reverse biased, charges in the P and N semiconductors are drawn away from the PN junction interface and hence forms the high resistance depletion zone.
- 3. OTHER NAMES The Varactor diode is also known as: ● Variable capacitance (Varicap) diode ● Voltage – Variable Capacitor (VCC) diode ● Tuning diode ● Variable reactance diode
- 5. BASIS OF OPERATION ● Operates in reverse bias and this gives rise to three regions. At either end of the diode are the P and N regions. However around the junction is the depletion region where no current carriers are available. As a result, current can be carried in the P and N regions, but the depletion region is an insulator. ● Same as capacitor construction. It has conductive plates separated by an insulating dielectric. ● The capacitance of a capacitor is dependent on a number of factors including the plate area, the dielectric constant of the insulator between the plates and the distance between the two plates. In the case of the varactor diode, it is possible to increase and decrease the width of the depletion region by changing the level of the reverse bias. This has the effect of changing the distance between the plates of the capacitor.
- 7. C – V CHARACTERISTICS
- 8. MATERIAL CONSTRUCTION Varactor diodes are manufactured with gallium arsenide. GaAs has a higher operating frequency (up to nearly 1000 GHz)
- 9. I – V CHARACTERISTICS
- 10. APPLICATIONS ● Variable reactor in microwave circuits. ● It is used in variable resonant tank LC circuit. Here C part is varied using varactor diode. ● AFC (Automatic Frequency Control) where in varactor diode is used to set LO signal. ● Varactor is used as frequency modulator in Radios and Television sets. ● It is used as frequency multiplier in microwave receiver LO. ● It is used as RF phase shifter.
- 11. CONCLUSION Varactor diodes in reverse bias operates as variable capacitor as reverse voltage varies, where: ● Depletion region : Dielectric (Insulator) ● P - N Regions : Plates of capacitor ● Width of Depletion region : Distance of separation
- 13. THANK YOU