Re: Rectification

On 3/11/2024 1:56 am, Liz Tuddenham wrote:

Cursitor Doom <cd@notformail.com> wrote:
 

On Sat, 2 Nov 2024 13:48:47 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
>

Cursitor Doom <cd@notformail.com> wrote:
>

... At still higher frequencies, the inherent capacitance
of the diode is leaving just a flat DC voltage with no longer any
peaks visible.

>
I would have thought, if the load was resistive, you would just see the
A.C. waveform, as the self-capacitance of the diode swamped out all the
other effects.  If you have a smoothing capacitor following the diode,
that would effectively be in series with the diode's self capacitance
and the two of them would act as a capacitive divider which
progressively shorted out the power supply as the frequency increased.

>
Yes, indeed, I'm sure a tank cap would be a short at relatively low
frequencies so I didn't envisage one for this particular mind
experiment.
I'd like to try it in Spice but I don't think the available diode
models are up to the job.

 Bear in mind that there are a lot of different types of diodes and some
are used as mixers up to SHF, so you might have to simulate low
infra-red before you noticed an non-diode behaviour with them.
Something like a 1N4001 would be more manageable.

I've seen the 1N4001 used as a varactor diode. It's not tightly specified for the role, but it didn't need to be in the application, where it balanced a capacitor bridge following the small alternating changes in a capacitance generated by small alternating changes in the pressure across a capacitative pressure gauge in a vortex shedding flow meter.
--
Bill Sloman, Sydney