R
RC
Guest
why microwave applications need devices with negative resistance?
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T
Tim Wescott
Guest
On 07/21/2010 07:25 AM, RC wrote:
resistance makes a tractable way to design an oscillator. And there are
devices that are useful at microwave frequencies that exhibit a negative
resistance effect.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
They don't. But treating a device as a one-port network with a negativewhy microwave applications need devices with negative resistance?
resistance makes a tractable way to design an oscillator. And there are
devices that are useful at microwave frequencies that exhibit a negative
resistance effect.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
J
John Larkin
Guest
On Wed, 21 Jul 2010 09:18:58 -0700, Tim Wescott <tim@seemywebsite.com>
wrote:
John
wrote:
I really miss tunnel diodes. Sob.On 07/21/2010 07:25 AM, RC wrote:
why microwave applications need devices with negative resistance?
They don't. But treating a device as a one-port network with a negative
resistance makes a tractable way to design an oscillator. And there are
devices that are useful at microwave frequencies that exhibit a negative
resistance effect.
John
T
Tim Wescott
Guest
On 07/21/2010 09:25 AM, John Larkin wrote:
Meter", which will need a complete rebuild if ever the tunnel diode
craps out).
http://en.wikipedia.org/wiki/Gunn_diode
http://en.wikipedia.org/wiki/IMPATT_diode
I believe that reflex klystrons and magnetrons also exhibit an apparent
negative resistance (or at least negative absorption) at their working
frequencies; this is what makes them oscillate.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
I missed out on it -- to young (except for my Heathkit "Tunnel DipOn Wed, 21 Jul 2010 09:18:58 -0700, Tim Wescott<tim@seemywebsite.com
wrote:
On 07/21/2010 07:25 AM, RC wrote:
why microwave applications need devices with negative resistance?
They don't. But treating a device as a one-port network with a negative
resistance makes a tractable way to design an oscillator. And there are
devices that are useful at microwave frequencies that exhibit a negative
resistance effect.
I really miss tunnel diodes. Sob.
Meter", which will need a complete rebuild if ever the tunnel diode
craps out).
http://en.wikipedia.org/wiki/Gunn_diode
http://en.wikipedia.org/wiki/IMPATT_diode
I believe that reflex klystrons and magnetrons also exhibit an apparent
negative resistance (or at least negative absorption) at their working
frequencies; this is what makes them oscillate.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
J
JW
Guest
On Wed, 21 Jul 2010 09:25:21 -0700 John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in Message id:
<nq7e46h4lum2916sdsra0qe2vcst6n43nb@4ax.com>:
of companies who still manufacture them, and the prices are outrageous. Is
there a reason why they are not so popular anymore? Were they always so
expensive?
I think they were more popular once but I guess that was before my time...
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in Message id:
<nq7e46h4lum2916sdsra0qe2vcst6n43nb@4ax.com>:
You got me curious. Taking a look around the net I only found a hand-fullI really miss tunnel diodes. Sob.
of companies who still manufacture them, and the prices are outrageous. Is
there a reason why they are not so popular anymore? Were they always so
expensive?
I think they were more popular once but I guess that was before my time...
M
Michael Black
Guest
On Thu, 22 Jul 2010, JW wrote:
better for doing things with.
They got a lot of press, certainly in the hobby publications, and that
got the attention of the hobbyists. They were novelties, and people
played with them when they were cheap.
But there was virtually nothing that you could do with tunnel diodes that
couldn't be done with other devices. Looking at the applications, the one
thing that seemed useful at the time was that they did operate at fairly
high frequencies, when other semiconductor devices were just moving up.
Once other devices came along to handle those higher frequencies, the
tunnel diode was just a novelty. Yes, you could use it as a mixer and
oscillator for a receiver, but you could do that with a transistor, and
you'd have better results with a single transistor for the mixer and a
single transistor for the oscillator. Tunnel diodes appealed to a certain
hobbyist mindset at the time, either because they were new so you'd be
playing with something that not everyone else was playing with yet, or
because they were portrayed in all kinds of simple circuits, for those
who wanted simple circuits.
They did not see a lot of commercial use. I have a Sony AM/FM portable
radio from the early sixties that makes mention of the Esaki diode (ie the
tunnel diode) on the front panel. I've not seen a schematic, and it's not
clear what the tunnel diode is in there for, maybe the mixer in the FM
section, maybe as an oscillator in the FM section, but it gave no
advantage to that radio, other than as a selling point, "hey, we've got
this new device that no other radio has".
What did happen is that it showed up in some esoteric test equipment,
I seem to recall someone mentioning when this had come up previously
that one oscilliscope used a tunnel diode as a trigger for the sweep,
and that's the sort of thing you'd need a tunnel diode for now. Not
for the function, but because you wanted to keep some commercial equipment
alive that happened to use a tunnel diode in that brief window when
tunnel diodes were "cool". If you can't get a replacement, then you
can no longer use that equipment.
There probably are some esoteric functions where the tunnel diode
can still be of value, I can't see why anyone would still make them
otherwise, but they just dont' serve a lot of purpose.
Michael
and soon after tunnel diodes arrived, other devices came along that wereOn Wed, 21 Jul 2010 09:25:21 -0700 John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in Message id:
nq7e46h4lum2916sdsra0qe2vcst6n43nb@4ax.com>:
I really miss tunnel diodes. Sob.
You got me curious. Taking a look around the net I only found a hand-full
of companies who still manufacture them, and the prices are outrageous. Is
there a reason why they are not so popular anymore? Were they always so
expensive?
I think they were more popular once but I guess that was before my time...
They had problems, and they didn't do much that other devices couldn't do,
better for doing things with.
They got a lot of press, certainly in the hobby publications, and that
got the attention of the hobbyists. They were novelties, and people
played with them when they were cheap.
But there was virtually nothing that you could do with tunnel diodes that
couldn't be done with other devices. Looking at the applications, the one
thing that seemed useful at the time was that they did operate at fairly
high frequencies, when other semiconductor devices were just moving up.
Once other devices came along to handle those higher frequencies, the
tunnel diode was just a novelty. Yes, you could use it as a mixer and
oscillator for a receiver, but you could do that with a transistor, and
you'd have better results with a single transistor for the mixer and a
single transistor for the oscillator. Tunnel diodes appealed to a certain
hobbyist mindset at the time, either because they were new so you'd be
playing with something that not everyone else was playing with yet, or
because they were portrayed in all kinds of simple circuits, for those
who wanted simple circuits.
They did not see a lot of commercial use. I have a Sony AM/FM portable
radio from the early sixties that makes mention of the Esaki diode (ie the
tunnel diode) on the front panel. I've not seen a schematic, and it's not
clear what the tunnel diode is in there for, maybe the mixer in the FM
section, maybe as an oscillator in the FM section, but it gave no
advantage to that radio, other than as a selling point, "hey, we've got
this new device that no other radio has".
What did happen is that it showed up in some esoteric test equipment,
I seem to recall someone mentioning when this had come up previously
that one oscilliscope used a tunnel diode as a trigger for the sweep,
and that's the sort of thing you'd need a tunnel diode for now. Not
for the function, but because you wanted to keep some commercial equipment
alive that happened to use a tunnel diode in that brief window when
tunnel diodes were "cool". If you can't get a replacement, then you
can no longer use that equipment.
There probably are some esoteric functions where the tunnel diode
can still be of value, I can't see why anyone would still make them
otherwise, but they just dont' serve a lot of purpose.
Michael
J
John Larkin
Guest
On Thu, 22 Jul 2010 14:47:37 -0400, Michael Black <et472@ncf.ca>
wrote:
used them extensively in their scopes, especially the multi-GHz
samplers. They were used in all sorts of circuits, especially
microwave trigger countdowns and TDR step generators.
Tunnel diodes would generate 20 picosecond steps when nothing else got
anywhere close.
with the little critters.
John
wrote:
TDs were the fastest parts, by far, for a decade at least. Tek and HPOn Thu, 22 Jul 2010, JW wrote:
On Wed, 21 Jul 2010 09:25:21 -0700 John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in Message id:
nq7e46h4lum2916sdsra0qe2vcst6n43nb@4ax.com>:
I really miss tunnel diodes. Sob.
You got me curious. Taking a look around the net I only found a hand-full
of companies who still manufacture them, and the prices are outrageous. Is
there a reason why they are not so popular anymore? Were they always so
expensive?
I think they were more popular once but I guess that was before my time...
They had problems, and they didn't do much that other devices couldn't do,
and soon after tunnel diodes arrived, other devices came along that were
better for doing things with.
They got a lot of press, certainly in the hobby publications, and that
got the attention of the hobbyists. They were novelties, and people
played with them when they were cheap.
But there was virtually nothing that you could do with tunnel diodes that
couldn't be done with other devices. Looking at the applications, the one
thing that seemed useful at the time was that they did operate at fairly
high frequencies, when other semiconductor devices were just moving up.
used them extensively in their scopes, especially the multi-GHz
samplers. They were used in all sorts of circuits, especially
microwave trigger countdowns and TDR step generators.
Tunnel diodes would generate 20 picosecond steps when nothing else got
anywhere close.
They sure did. Look at a Tek 547 schematic. Or a 1S2. They're filthyOnce other devices came along to handle those higher frequencies, the
tunnel diode was just a novelty. Yes, you could use it as a mixer and
oscillator for a receiver, but you could do that with a transistor, and
you'd have better results with a single transistor for the mixer and a
single transistor for the oscillator. Tunnel diodes appealed to a certain
hobbyist mindset at the time, either because they were new so you'd be
playing with something that not everyone else was playing with yet, or
because they were portrayed in all kinds of simple circuits, for those
who wanted simple circuits.
They did not see a lot of commercial use.
with the little critters.
John
W
whit3rd
Guest
On Jul 22, 11:47 am, Michael Black <et...@ncf.ca> wrote:
decades
were based on tunnel diodes. Most tunnel diodes were Ge (some now
are GaAs) though, and the Ge production lines became ... ineconomic.
They were never 'popular' because there weren't any good ways to
limit the GHz gain, and lots of folk couldn't debug 'em if/when the
oscillations
got out of hand.
Not exactly true; the bulk of UHF tuners in TVs for a couple ofOn Thu, 22 Jul 2010, JW wrote:
On Wed, 21 Jul 2010 09:25:21 -0700 John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote in Message id:
nq7e46h4lum2916sdsra0qe2vcst6n4...@4ax.com>:
I really miss tunnel diodes. Sob.
You got me curious. Taking a look around the net I only found a hand-full
of companies who still manufacture them, and the prices are outrageous. Is
there a reason why they are not so popular anymore? Were they always so
expensive?
I think they were more popular once but I guess that was before my time...
They had problems, and they didn't do much that other devices couldn't do,
and soon after tunnel diodes arrived, other devices came along that were
better for doing things with.
decades
were based on tunnel diodes. Most tunnel diodes were Ge (some now
are GaAs) though, and the Ge production lines became ... ineconomic.
They were never 'popular' because there weren't any good ways to
limit the GHz gain, and lots of folk couldn't debug 'em if/when the
oscillations
got out of hand.