What is a Varicap diode used for?
Varactor or varicap diodes are used mainly in radio frequency or RF circuits to provide voltage controlled variable capacitance. These electronic componenta can be used in a whole variety of ways where a capacitance level needs to be controlled by a voltage.
How does a 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.
Which diodes are used as tuning diodes?
The varactor diodes are used in tuning circuits, they are used as a replacement for classic capacitor tuning in old FM radio. They are used in tank circuits or LC circuits. They are used in signal modulation and demodulation processes. They are used as frequency multipliers.
What is the use of director diode in radio receiver?
The diode detector is the simplest form of detector or demodulator used for AM demodulation – it detects the AM signal envelope. The diode detector is the simplest and most basic form of amplitude modulation, AM signal detector and it detects the envelope of the AM signal.
When bias applied to a Varicap diode in increased then capacitance?
Characteristic of Varactor Diode The graph shows that when the reverse bias voltage increases the depletion region increases, and the capacitance of the diode reduces.
When bias applied to a varicap diode in increased then capacitance?
Which diode is used for tuning purpose?
A varactor diode is a simple variable capacitor that allows oscillator circuits and other circuits to be easily tuned by applying a voltage. These diodes have a similar structure as a p-n diode; the structure of a varactor diode is rather simple and illustrates its power as a component with nonlinear reactance.
In what condition a Varicap works?
It always works in reverse bias condition and is a voltage-dependent semiconductor device. Varactor diode is known by several names as Varicap, Voltcap, Voltage variable capacitance, or Tunning diode.
When pn junction diode is forward bias forward current is dominated by?
diffusion
There are two majority carriers associated with a pn junction, one on each side. As the device is in forward bias, the current will be dominated by diffusion. As it is p+n, it will be dominated by hole diffusion over electron diffusion.
Where we use PN junction diode?
p-n junction diode can be used as a photodiode as the diode is sensitive to the light when the configuration of the diode is reverse-biased. It can be used as a solar cell….Applications of PN Junction Diode.
| Semiconductor Diode | Zener Diode |
|---|---|
| Extrinsic Semiconductors | Electric Field Lines |
How do you identify a PN junction diode?
The PN junction region of a Junction Diode has the following important characteristics:
- Semiconductors contain two types of mobile charge carriers, “Holes” and “Electrons”.
- The holes are positively charged while the electrons negatively charged.
What happens when a varicap diode is applied?
When a varactor or varicap diode is applied with a rising reverse bias potential, results in an increase in the depletion width of the device, which in turn causes its transition capacitance to decrease. The following image shows the typical characteristics response of a varactor diode.
How to calculate the capacitance of a varactor diode?
Normally, the range for the applied reverse bias voltage VR for a variable voltage capacitance diode is restricted to 20 V. With regard to the applied reverse bias voltage, the transition capacitance can be approximated using the formula: CT = K / (VT + VR)n
Are there any high capacitance varicaps for HF band?
While low capacitance varicaps for VHF and UHF circuits are still reasonably easy to find, high capacitance varicaps for HF and AM band designs are as rare as unicorn’s tusks. Those wonderful Philips BB212 dual varicap diodes appear to have become nigh on unobtainable.
What can a reverse biased varicap be used for?
In the case of a reverse biased varicap, since minimal current can flow in a good reverse biased diode, the result is an insulating layer between two conducting silicon layers. This layer widens with increasing reverse bias voltage. The result is a device which can be used as a voltage variable capacitor.