Dr. Grok wrote:
Maybe I'm confusing this with something else but I always thought 1N4007's
were 1000 V PIV, 1 A rectifiers.

I believe "any" diode has varactor characteristics to some extent but if you
need a varactor you'd be better off using one designed as a varactor.

Dr. G.



In article , JE wrote:

The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors?

And how about zener diodes?

JE
All diodes exhibit varactor and zener traits but not all are stable
as such. All diodes when reverse biased exhibit a value of capacitance
across them. In most cases it's usually quite small, less than 5 to 10pf.
Increase the reverse bias and the capacitance goes down. At very high frequencies
the capacitance change is enough to make a useful tuning diode. If you need
a varactor to work at medium to high frequencies the tuning effect won't be
very useful and you should use a true varactor diode. Such diodes have
either larger areas, or thinner substrates to increase th capacitance.

Any diode will work as a Zener, the zener voltage is where the reverse breakdown
occurs. In a true Zener, the breakdown voltage is stable over a large range
of current without the diode self destructing. Using a common diode as a zener
requires limiting the reverse current to a small value, but if the current isn't
large enough the zener voltage won't be stable.

And yes the 1n4007 is a 1000 vpiv rectifier diode. It also makes a good
rf switching diode thanks to it's PIN like structure. It's also quite cheap.