need recommendation on diode variable capacitor

[amicloud]

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

 

[D.A.(Tony)Stewart]

Q reduces with increasing frequency in Silicon. I expect 10 to 30 @2GHz

Consider Hyperabrupt Junction diodes https://www.skyworksinc.com/uploads/documents/SMV1405_SMV1430_Series_200068P.pdf

Or MOSFET junctions or Gunn Diodes maybe

 

[jiripolivka]

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.

 

[D.A.(Tony)Stewart]

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.

 

[jiripolivka]

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.

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.