# Varicap @ mV or even µV?

Discussion in 'General Electronics Discussion' started by Moritz, Dec 12, 2015.

1. ### Moritz

3
0
Dec 12, 2015
Hi there,

I'm curious. Do varicaps exists, that can operate with mV or even µV?
And what should I search for?

Thanks and best regards,
Moritz

2. ### davennModerator

13,833
1,950
Sep 5, 2009
hi there
varicap diodes, I assume you are referring to ?

3. ### Moritz

3
0
Dec 12, 2015
Yes, I'm referring to variable capacity diodes.

And I can't really tell you what I'm intending to do. Junst wondering if there are any, that can change theire capacity by milivolts of DC bias?

4. ### davennModerator

13,833
1,950
Sep 5, 2009
you would have to look at the datasheets for specific types to get an idea
of their change in capacitance relative to the voltage ... that data will be graphed
and they will all be different

Dave

5. ### Moritz

3
0
Dec 12, 2015
Yeah, I know that, that's why I'm asking. Because the datasheets I previously looked at don't have any data below several hundred of milivolts. So I'm wondering if maybe you guys know some varicaps that can operate in such magnitude of voltage...

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,496
2,837
Jan 21, 2010
well, they will very definitely resound to a signal in the millivolt or microvolt range, but this would need to be added to a constant voltage, and the amount of variation would be tiny.

Amplifying that small signal before applying it tho the diode would allow you to change the capacitance more.

The reason you need a relatively large voltage change to affect the capacitance is that you don't want the signal itself to change the capacitance (typically).

If your control voltage was significant at a might change then your signal would need to be even smaller.

7. ### dorke

2,342
665
Jun 20, 2015
Moritz,
What is the frequency range you are going to operate at?

13,833
1,950
Sep 5, 2009