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need recommendation on diode variable capacitor

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amicloud

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Dear all,
I need variable capacitor, working at 1-2GHz, with capacitance of 1-5pF. I hope the Q
is high enough, such as 200. Can you recommend? Thanks.

Yun
 

Including MOSFET junctions or Gunn diodes is plainly wrong!
The variable-capacitance diodes are "varicaps" and offered by Agilent, Skyworks an many other makers.
Hyper=abrupt junction diodes are "vaactors" and instead of tuning resonant circuits they are used in power frequency multipliers.
Gunn devices are no diodes, the semiconductor thin layer is passed by a high current density which generates microwave oscillations. They have no junction like diodes.
 
I disagree jiripolivka.. Mosfets have **broken link removed**. and Gunn Diodes are used for 8~30GHz as high Q resonant oscillators with a varactor diode using the negative resistance property of the Gunn diode, also known as a transferred electron device (TED),

The diode series is recommended for the varactor is suitable.
 
Last edited:

SunnySkyguy said:
I disagree jiripolivka.. Mosfets have **broken link removed**. and Gunn Diodes are used for 8~30GHz as high Q resonant oscillators with a varactor diode using the negative resistance property of the Gunn diode, also known as a transferred electron device (TED),

The diode series is recommended for the varactor is suitable.
Click to expand...

Dear SunnyGuy:

1. MOSFETs are used with varactors in circuits but not "as varactors". MOSFETs are used as OSCILLATORS that are tuned by varactors.
2. I repeat that Gunn devices are NOT DIODES. Gunn device has never a "high Q" but serves as a negative resistance causing a high Q resonator to keep a precise frequency. TED is another name for Gunn devices.

Varicaps are junction diodes used to tune resonant circuits by varying reverse voltage. They are made with small ( 0.5...10 pF) range to large (10-300 pF) range, and used in AM/FM receivers.

Varactors are hyper-abrupt junction diodes. They can be used also for tuning resonators but the preferred applications are frequency multiplication and harmonic comb generation.
 

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