What is a Varicap diode used for?
What is a Varicap diode used for?
Tuning circuits. Generally the use of a varicap diode in a circuit requires connecting it to a tuned circuit, usually in parallel with any existing capacitance or inductance. A DC voltage is applied as reverse bias across the varicap to alter its capacitance.
How does Varicap diode work?
A varactor diode is designed to store electric charge not to conduct electric current. So varactor diode should always be operated in reverse bias. When a reverse bias voltage is applied, the electrons from n-region and holes from p-region moves away from the junction.
What is meant by varactor diode?
A varactor diode is a p-n-junction diode, in which internal capacitance can be altered as a result of the application of reverse bias voltage. The varactor diode works in the reverse bias condition. It is also known as Varicap diode or voltCap diode indicating varying capacitance.
Is a diode a variable capacitor?
Variable capacitance diodes are produced and characterized for use as electronically-variable capacitors, and are widely used in tuning and frequency synthesis applications.
What is the difference between varicap and varactor diodes?
The name varactor meaning variable reactor, or reactance, and varicap meaning variable capacitance (vari-cap). Varactor diodes are widely used within many RF designs. They provide a method of varying the capacitance within a circuit by the application of a control voltage.
How is the depletion zone of a varicap determined?
Varactors are operated in a reverse-biased state, so no DC current flows through the device. The amount of reverse bias controls the thickness of the depletion zone and therefore the varactor’s junction capacitance. Generally, the depletion region thickness is proportional to the square root of the applied voltage,…
Why are varicaps used in hyperabrupt junction profiles?
For hyperabrupt junction profile capacitance change is more non-linear, but hyperabrupt varicaps have larger capacitance variation and can work with lower voltages. All diodes exhibit this variable junction capacitance, but varactors are manufactured to exploit the effect and increase the capacitance variation.
When does a varicap have a high capacitance a low impedance?
When in the high capacitance state, usually with low or no bias, they present a low impedance path to RF, whereas when reverse biased their capacitance abruptly decreases and their RF impedance increases.
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