Greetings mesdammes et messureses,
Say I'm using a regular jelly bean diode to rectify an AC waveform to
a light load. Everything's hunky dory at 50hz and the negative
portions of the wave are neatly removed. I up the frequency to say
1khz and all is still well.... and repeat. Eventually I will notice
that there's insufficient recovery time for the diode to function as
it formerly was. At still higher frequencies, the inherent capacitance
of the diode is leaving just a flat DC voltage with no longer any
peaks visible. If I keep going up and up in frequency, will this
situation continue indefinitely or will I eventually run into some
weird unexpected effects like negative resistance/parametric
amplification etc etc?
PS: Please don't suggest using a fast recovery diode as that's not
what the question is getting at. I'm not after a solution to a
problem, just an answer to this entirely theoretical question.
... At still higher frequencies, the inherent capacitance
of the diode is leaving just a flat DC voltage with no longer any
peaks visible.
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.
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.
Greetings mesdammes et messureses,
Say I'm using a regular jelly bean diode to rectify an AC waveform to
a light load. Everything's hunky dory at 50hz and the negative
portions of the wave are neatly removed. I up the frequency to say
1khz and all is still well.... and repeat. Eventually I will notice
that there's insufficient recovery time for the diode to function as
it formerly was. At still higher frequencies, the inherent capacitance
of the diode is leaving just a flat DC voltage with no longer any
peaks visible. If I keep going up and up in frequency, will this
situation continue indefinitely or will I eventually run into some
weird unexpected effects like negative resistance/parametric
amplification etc etc?
CD.
PS: Please don't suggest using a fast recovery diode as that's not
what the question is getting at. I'm not after a solution to a
problem, just an answer to this entirely theoretical quesition.
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.
On Sat, 02 Nov 2024 12:34:44 +0000, Cursitor Doom <cd@notformail.com>
wrote:
Greetings mesdammes et messureses,
Say I'm using a regular jelly bean diode to rectify an AC waveform to
a light load. Everything's hunky dory at 50hz and the negative
portions of the wave are neatly removed. I up the frequency to say
1khz and all is still well.... and repeat. Eventually I will notice
that there's insufficient recovery time for the diode to function as
it formerly was. At still higher frequencies, the inherent capacitance
of the diode is leaving just a flat DC voltage with no longer any
peaks visible. If I keep going up and up in frequency, will this
situation continue indefinitely or will I eventually run into some
weird unexpected effects like negative resistance/parametric
amplification etc etc?
CD.
PS: Please don't suggest using a fast recovery diode as that's not
what the question is getting at. I'm not after a solution to a
problem, just an answer to this entirely theoretical quesition.
Eventually the ESL of the diode will series resonate with its
capacitance, and beyond that it's an inductor.
By that time, it's not much of a diode. In a PN silicon diode the
carriers can't move very fast so it starts to look ohmic at high
frequencies. PN diodes have both reverse and "forward recovery" time
delays.
I've used SiC diodes for fast high-voltage things and they are much
better than silicon.
It is an interesting problem, how to make a power rectifier at very
high frequencies. It's been proposed to put solar arrays in orbit and
beam the power down as microwaves, into "rectennas" on the ground.
They must have some sorts of diodes in mind.
The step recovery effect is cool too. Look up "drift step recovery
diode" aka Grekhov diode for some other interesting effects. I made
one thing that forward biases a power diode at +50 volts for a while
and then reverses it at a couple hundred amps. I didn't sell many but
it was fun.
https://www.dropbox.com/scl/fi/7r128d5fny7kj403ozk5q/Neon_5.JPG?rlkey=6gz93k2xr1bvsxljaxomd8swg&raw=1
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.
On Sat, 02 Nov 2024 08:15:17 -0700, john larkin <JL@gct.com> wrote:
On Sat, 02 Nov 2024 12:34:44 +0000, Cursitor Doom <cd@notformail.com>
wrote:
Greetings mesdammes et messureses,
Say I'm using a regular jelly bean diode to rectify an AC waveform to
a light load. Everything's hunky dory at 50hz and the negative
portions of the wave are neatly removed. I up the frequency to say
1khz and all is still well.... and repeat. Eventually I will notice
that there's insufficient recovery time for the diode to function as
it formerly was. At still higher frequencies, the inherent capacitance
of the diode is leaving just a flat DC voltage with no longer any
peaks visible. If I keep going up and up in frequency, will this
situation continue indefinitely or will I eventually run into some
weird unexpected effects like negative resistance/parametric
amplification etc etc?
CD.
PS: Please don't suggest using a fast recovery diode as that's not
what the question is getting at. I'm not after a solution to a
problem, just an answer to this entirely theoretical quesition.
Eventually the ESL of the diode will series resonate with its
capacitance, and beyond that it's an inductor.
By that time, it's not much of a diode. In a PN silicon diode the
carriers can't move very fast so it starts to look ohmic at high
frequencies. PN diodes have both reverse and "forward recovery" time
delays.
I've used SiC diodes for fast high-voltage things and they are much
better than silicon.
It is an interesting problem, how to make a power rectifier at very
high frequencies. It's been proposed to put solar arrays in orbit and
beam the power down as microwaves, into "rectennas" on the ground.
They must have some sorts of diodes in mind.
The step recovery effect is cool too. Look up "drift step recovery
diode" aka Grekhov diode for some other interesting effects. I made
one thing that forward biases a power diode at +50 volts for a while
and then reverses it at a couple hundred amps. I didn't sell many but
it was fun.
https://www.dropbox.com/scl/fi/7r128d5fny7kj403ozk5q/Neon_5.JPG?rlkey=6gz93k2xr1bvsxljaxomd8swg&raw=1
Cool. Like everyone else here I suppose, I have thousands of diodes of
all kinds, some more easy to identify than others. I have the
capability to characterize them for their different high speed
attributes, but doing so *properly* would take up huge amounts of time
and sadly I just can't spare it. Life gets shorter every year it
seems.
On 3/11/2024 6:03 am, Cursitor Doom wrote:
On Sat, 02 Nov 2024 08:15:17 -0700, john larkin <JL@gct.com> wrote:
On Sat, 02 Nov 2024 12:34:44 +0000, Cursitor Doom <cd@notformail.com>
wrote:
Greetings mesdammes et messureses,
Say I'm using a regular jelly bean diode to rectify an AC waveform to
a light load. Everything's hunky dory at 50hz and the negative
portions of the wave are neatly removed. I up the frequency to say
1khz and all is still well.... and repeat. Eventually I will notice
that there's insufficient recovery time for the diode to function as
it formerly was. At still higher frequencies, the inherent capacitance >>>> of the diode is leaving just a flat DC voltage with no longer any
peaks visible. If I keep going up and up in frequency, will this
situation continue indefinitely or will I eventually run into some
weird unexpected effects like negative resistance/parametric
amplification etc etc?
CD.
PS: Please don't suggest using a fast recovery diode as that's not
what the question is getting at. I'm not after a solution to a
problem, just an answer to this entirely theoretical quesition.
Eventually the ESL of the diode will series resonate with its
capacitance, and beyond that it's an inductor.
By that time, it's not much of a diode. In a PN silicon diode the
carriers can't move very fast so it starts to look ohmic at high
frequencies. PN diodes have both reverse and "forward recovery" time
delays.
I've used SiC diodes for fast high-voltage things and they are much
better than silicon.
It is an interesting problem, how to make a power rectifier at very
high frequencies. It's been proposed to put solar arrays in orbit and
beam the power down as microwaves, into "rectennas" on the ground.
They must have some sorts of diodes in mind.
The step recovery effect is cool too. Look up "drift step recovery
diode" aka Grekhov diode for some other interesting effects. I made
one thing that forward biases a power diode at +50 volts for a while
and then reverses it at a couple hundred amps. I didn't sell many but
it was fun.
https://www.dropbox.com/scl/fi/7r128d5fny7kj403ozk5q/Neon_5.JPG?rlkey=6gz93k2xr1bvsxljaxomd8swg&raw=1
Cool. Like everyone else here I suppose, I have thousands of diodes of
all kinds, some more easy to identify than others. I have the
capability to characterize them for their different high speed
attributes, but doing so *properly* would take up huge amounts of time
and sadly I just can't spare it. Life gets shorter every year it
seems.
It would take even longer for you to learn enough to be able to classify
them properly.
Step recovery diodes are fun, as John Larkin points out, but even if you >spend the money to buy one that is properly characterised for the task
you have to wait a while for the snap-off edge that you want and the
stored charged that works the magic isn't all the well-defined.
On Sun, 3 Nov 2024 13:53:49 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 3/11/2024 6:03 am, Cursitor Doom wrote:
On Sat, 02 Nov 2024 08:15:17 -0700, john larkin <JL@gct.com> wrote:
On Sat, 02 Nov 2024 12:34:44 +0000, Cursitor Doom <cd@notformail.com>
wrote:
Greetings mesdammes et messureses,
Say I'm using a regular jelly bean diode to rectify an AC waveform to >>>>> a light load. Everything's hunky dory at 50hz and the negative
portions of the wave are neatly removed. I up the frequency to say
1khz and all is still well.... and repeat. Eventually I will notice
that there's insufficient recovery time for the diode to function as >>>>> it formerly was. At still higher frequencies, the inherent capacitance >>>>> of the diode is leaving just a flat DC voltage with no longer any
peaks visible. If I keep going up and up in frequency, will this
situation continue indefinitely or will I eventually run into some
weird unexpected effects like negative resistance/parametric
amplification etc etc?
CD.
PS: Please don't suggest using a fast recovery diode as that's not
what the question is getting at. I'm not after a solution to a
problem, just an answer to this entirely theoretical quesition.
Eventually the ESL of the diode will series resonate with its
capacitance, and beyond that it's an inductor.
By that time, it's not much of a diode. In a PN silicon diode the
carriers can't move very fast so it starts to look ohmic at high
frequencies. PN diodes have both reverse and "forward recovery" time
delays.
I've used SiC diodes for fast high-voltage things and they are much
better than silicon.
It is an interesting problem, how to make a power rectifier at very
high frequencies. It's been proposed to put solar arrays in orbit and
beam the power down as microwaves, into "rectennas" on the ground.
They must have some sorts of diodes in mind.
The step recovery effect is cool too. Look up "drift step recovery
diode" aka Grekhov diode for some other interesting effects. I made
one thing that forward biases a power diode at +50 volts for a while
and then reverses it at a couple hundred amps. I didn't sell many but
it was fun.
https://www.dropbox.com/scl/fi/7r128d5fny7kj403ozk5q/Neon_5.JPG?rlkey=6gz93k2xr1bvsxljaxomd8swg&raw=1
Cool. Like everyone else here I suppose, I have thousands of diodes of
all kinds, some more easy to identify than others. I have the
capability to characterize them for their different high speed
attributes, but doing so *properly* would take up huge amounts of time
and sadly I just can't spare it. Life gets shorter every year it
seems.
It would take even longer for you to learn enough to be able to classify
them properly.
Step recovery diodes are fun, as John Larkin points out, but even if you
spend the money to buy one that is properly characterised for the task
you have to wait a while for the snap-off edge that you want and the
stored charged that works the magic isn't all the well-defined.
Pretty good for generating a comb, though. I would guess there are
more varieties of diode than any other discrete component there is.
Quite a remarkable little device and - usually - trivially cheap.
Pretty good for generating a comb, though. I would guess there are
more varieties of diode than any other discrete component there is.
Quite a remarkable little device and - usually - trivially cheap.
On Sun, 3 Nov 2024 13:53:49 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 3/11/2024 6:03 am, Cursitor Doom wrote:
On Sat, 02 Nov 2024 08:15:17 -0700, john larkin <JL@gct.com> wrote:
On Sat, 02 Nov 2024 12:34:44 +0000, Cursitor Doom <cd@notformail.com>
wrote:
Greetings mesdammes et messureses,
Say I'm using a regular jelly bean diode to rectify an AC waveform to >>>>> a light load. Everything's hunky dory at 50hz and the negative
portions of the wave are neatly removed. I up the frequency to say
1khz and all is still well.... and repeat. Eventually I will notice
that there's insufficient recovery time for the diode to function as >>>>> it formerly was. At still higher frequencies, the inherent capacitance >>>>> of the diode is leaving just a flat DC voltage with no longer any
peaks visible. If I keep going up and up in frequency, will this
situation continue indefinitely or will I eventually run into some
weird unexpected effects like negative resistance/parametric
amplification etc etc?
CD.
PS: Please don't suggest using a fast recovery diode as that's not
what the question is getting at. I'm not after a solution to a
problem, just an answer to this entirely theoretical quesition.
Eventually the ESL of the diode will series resonate with its
capacitance, and beyond that it's an inductor.
By that time, it's not much of a diode. In a PN silicon diode the
carriers can't move very fast so it starts to look ohmic at high
frequencies. PN diodes have both reverse and "forward recovery" time
delays.
I've used SiC diodes for fast high-voltage things and they are much
better than silicon.
It is an interesting problem, how to make a power rectifier at very
high frequencies. It's been proposed to put solar arrays in orbit and
beam the power down as microwaves, into "rectennas" on the ground.
They must have some sorts of diodes in mind.
The step recovery effect is cool too. Look up "drift step recovery
diode" aka Grekhov diode for some other interesting effects. I made
one thing that forward biases a power diode at +50 volts for a while
and then reverses it at a couple hundred amps. I didn't sell many but
it was fun.
https://www.dropbox.com/scl/fi/7r128d5fny7kj403ozk5q/Neon_5.JPG?rlkey=6gz93k2xr1bvsxljaxomd8swg&raw=1
Cool. Like everyone else here I suppose, I have thousands of diodes of
all kinds, some more easy to identify than others. I have the
capability to characterize them for their different high speed
attributes, but doing so *properly* would take up huge amounts of time
and sadly I just can't spare it. Life gets shorter every year it
seems.
It would take even longer for you to learn enough to be able to classify >>them properly.
Step recovery diodes are fun, as John Larkin points out, but even if you >>spend the money to buy one that is properly characterised for the task
you have to wait a while for the snap-off edge that you want and the
stored charged that works the magic isn't all the well-defined.
Pretty good for generating a comb, though. I would guess there are
more varieties of diode than any other discrete component there is.
Quite a remarkable little device and - usually - trivially cheap.
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.
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