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Topic: building a digitally controlled variable capacitor (Read 911 times) previous topic - next topic

mightyruler

the digitally controlled variable capacitor  I was looking at getting is still listed on digikey, but is no longer manufactured. so, looking at the data sheet, it looks simple to build. the question i have, is what is the control circuit called? it has something to do with a single in controlling transistors that connect/disconnect about 5 capacitors. It is a simple circuit, and seems that there should be lots of option already designed and tested.

CrossRoads

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

mightyruler

http://www.intersil.com/content/dam/Intersil/documents/fn81/fn8156.pdf

CrossRoads

Looks like plenty available at Mouser
http://www.mouser.com/Search/Refine.aspx?Keyword=x90100
"New At Mouser" hardly seems to indicate discontinued.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

mightyruler

thank you. if i can get it, then it will be the easy way and i was looking forward to building a bulky circuit.

Runaway Pancake

7.5 - 14.5 pF

How about "Fun WIth Varactor Diodes"?
"Hello, I must be going..."
"You gotta fight -- for your right -- to party!"
Don't react - Read.
"Who is like unto the beast? who is able to make war with him?"

JohnLincoln

The bulky circuit you were looking forwards to building would have had far more stray capacitance than the 7.5pF to 14.5pF of the actual device.

Paul__B

Perhaps you should remind us of what it is you propose to do with this digitally controlled variable capacitor.

If it is in regard to controlling the frequency of an oscillator as you have previously implied, then it is almost certainly an inappropriate approach as direct digital synthesis (of sinewaves, no less) is much more effectively and reliably performed, for which ICs are readily available.

mightyruler


Paul__B


nilton61

This can be done with a 4066 quad analog switch and some capacitors

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