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Old 24th May 2017, 6:17 am   #21
Synchrodyne
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Default Re: Varicap tuning

It would appear that the name “varicap” was first used by Pacific Semiconductors Inc., who released a range of such devices in 1958. There was a brief mention in Radio-Electronics for 1958 January, page 45. This was followed with a 3-page article “Using the Varicap” in the 1958 May issue, page 57ff.

These Radio-Electronics articles are available at: http://www.americanradiohistory.com/...aster_Page.htm.


Cheers,
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Old 25th May 2017, 8:05 am   #22
trsomian
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Default Re: Varicap tuning

I have been wondering for a while how well photodiodes would work as varicaps, obviously painted black to stop the light getting in. The point is, of course, that the area of the junction of some of them is vastly greater than most diodes, so that they capture more photons, so presumably have more capacitance. I am not thinking of the PIN photodiodes, of course. I must try it sometime when I have nothing else to do!
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Old 25th May 2017, 9:20 am   #23
MrBungle
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Default Re: Varicap tuning

Good idea. That's kind of the inverse of the old OC transistors i.e. remove the paint to add new and interesting features
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Old 26th May 2017, 5:26 pm   #24
G6Tanuki
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Default Re: Varicap tuning

Quote:
Originally Posted by trsomian View Post
I have been wondering for a while how well photodiodes would work as varicaps, obviously painted black to stop the light getting in. The point is, of course, that the area of the junction of some of them is vastly greater than most diodes, so that they capture more photons, so presumably have more capacitance. I am not thinking of the PIN photodiodes, of course. I must try it sometime when I have nothing else to do!
I've certainly had experience of a glass-encapsulated transistor used in a FM radio signal-frequency strip where a scratched case caused a 'buzz' when strongly illuminated by the fluorescent light in an illuminated magnifier.

Didn't do it on MW/LW. A new transistor was fitted.
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