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Sure. Works fine, but you get N * Rds(on) as it were, and if your load is
50 ohms or whatever regardless of stack height, well...
Tim
Sure. Works fine, but you get N * Rds(on) as it were, and if your load
is 50 ohms or whatever regardless of stack height, well...
Sure. Works fine, but you get N * Rds(on) as it were, and if your load
is 50 ohms or whatever regardless of stack height, well...
Sure. Works fine, but you get N * Rds(on) as it were, and if your load
is 50 ohms or whatever regardless of stack height, well...
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization whichHas anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization whichHas anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
On Wed, 22 Jul 2020 02:54:38 -0400, bitrex <user@example.net> wrote:
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
Cool, 1964, obviously done on a fairly worn-out typewriter.
The Zetex parts are, to my knowledge, the only transistors
specifically designed to avalanche. They are apparently made on an
ancient Russian fab line, probably all diffused. Epitaxial transistors
seem to not avalanche much.
But given the Zetex monolopy, I\'m more interested in circuits and
physical PCB topologies, and especially actual experience.
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
Interesting, but I\'m not designing semiconductors, especially not with
germanium.
The old HP and Tek sampling scopes seemed to use selected 2N-type
parts. Biased to maybe 60 volts or so, they could be triggered to make
maybe a 30 volt sampling spike under 100 ps wide. The 7S14 uses an
avalanche transistor to sample two channels and gets 2 GHz typical
bandwidth.
The old transistors roughly half-discharged the available voltage. HP
and Tek no doubt got selected parts from the makers; a random 2Nxxxx
would be unpredictable. The Zetex parts fire like an SCR, all the way
down to zero volts/shorted, and the SOT23s can dump 60 amps in around
a nanosecond. That\'s worth $6.
On Wed, 22 Jul 2020 02:54:38 -0400, bitrex <user@example.net> wrote:
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
Cool, 1964, obviously done on a fairly worn-out typewriter.
The Zetex parts are, to my knowledge, the only transistors
specifically designed to avalanche. They are apparently made on an
ancient Russian fab line, probably all diffused. Epitaxial transistors
seem to not avalanche much.
But given the Zetex monolopy, I\'m more interested in circuits and
physical PCB topologies, and especially actual experience.
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
Interesting, but I\'m not designing semiconductors, especially not with
germanium.
The old HP and Tek sampling scopes seemed to use selected 2N-type
parts. Biased to maybe 60 volts or so, they could be triggered to make
maybe a 30 volt sampling spike under 100 ps wide. The 7S14 uses an
avalanche transistor to sample two channels and gets 2 GHz typical
bandwidth.
The old transistors roughly half-discharged the available voltage. HP
and Tek no doubt got selected parts from the makers; a random 2Nxxxx
would be unpredictable. The Zetex parts fire like an SCR, all the way
down to zero volts/shorted, and the SOT23s can dump 60 amps in around
a nanosecond. That\'s worth $6.
On 7/22/2020 10:01 AM, jlarkin@highlandsniptechnology.com wrote:
On Wed, 22 Jul 2020 02:54:38 -0400, bitrex <user@example.net> wrote:
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
Cool, 1964, obviously done on a fairly worn-out typewriter.
The Zetex parts are, to my knowledge, the only transistors
specifically designed to avalanche. They are apparently made on an
ancient Russian fab line, probably all diffused. Epitaxial transistors
seem to not avalanche much.
But given the Zetex monolopy, I\'m more interested in circuits and
physical PCB topologies, and especially actual experience.
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
Interesting, but I\'m not designing semiconductors, especially not with
germanium.
I don\'t think the math for silicon diffused transistors would be that
different vs. germanium, just different fudge-factors
The old HP and Tek sampling scopes seemed to use selected 2N-type
parts. Biased to maybe 60 volts or so, they could be triggered to make
maybe a 30 volt sampling spike under 100 ps wide. The 7S14 uses an
avalanche transistor to sample two channels and gets 2 GHz typical
bandwidth.
The ol\' 2D21 thyratrons, gas tube relay triggers for like jukeboxes and
stuff I guess, had very fast (ionization? de-ionization?) times for
their era. I dunno what the equivalent slew rate is exactly but the
rising edge on a relaxation sawtooth is fast enough that divided down
the usual jellybean opamps as unity-buffers with GBWs of 10s of MHz and
10 or 20 volt/usec slew rates can\'t keep up.
The old transistors roughly half-discharged the available voltage. HP
and Tek no doubt got selected parts from the makers; a random 2Nxxxx
would be unpredictable. The Zetex parts fire like an SCR, all the way
down to zero volts/shorted, and the SOT23s can dump 60 amps in around
a nanosecond. That\'s worth $6.
I saw a contract job posting where the client wanted circuit to charge a
400n capacitance to 60V in 40 nanoseconds. Maybe you want that job. I
don\'t want that job. Particularly if they\'re from the Middle East
On 7/22/2020 10:01 AM, jlarkin@highlandsniptechnology.com wrote:
On Wed, 22 Jul 2020 02:54:38 -0400, bitrex <user@example.net> wrote:
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
Cool, 1964, obviously done on a fairly worn-out typewriter.
The Zetex parts are, to my knowledge, the only transistors
specifically designed to avalanche. They are apparently made on an
ancient Russian fab line, probably all diffused. Epitaxial transistors
seem to not avalanche much.
But given the Zetex monolopy, I\'m more interested in circuits and
physical PCB topologies, and especially actual experience.
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
Interesting, but I\'m not designing semiconductors, especially not with
germanium.
I don\'t think the math for silicon diffused transistors would be that
different vs. germanium, just different fudge-factors
The old HP and Tek sampling scopes seemed to use selected 2N-type
parts. Biased to maybe 60 volts or so, they could be triggered to make
maybe a 30 volt sampling spike under 100 ps wide. The 7S14 uses an
avalanche transistor to sample two channels and gets 2 GHz typical
bandwidth.
The ol\' 2D21 thyratrons, gas tube relay triggers for like jukeboxes and
stuff I guess, had very fast (ionization? de-ionization?) times for
their era. I dunno what the equivalent slew rate is exactly but the
rising edge on a relaxation sawtooth is fast enough that divided down
the usual jellybean opamps as unity-buffers with GBWs of 10s of MHz and
10 or 20 volt/usec slew rates can\'t keep up.
The old transistors roughly half-discharged the available voltage. HP
and Tek no doubt got selected parts from the makers; a random 2Nxxxx
would be unpredictable. The Zetex parts fire like an SCR, all the way
down to zero volts/shorted, and the SOT23s can dump 60 amps in around
a nanosecond. That\'s worth $6.
I saw a contract job posting where the client wanted circuit to charge a
400n capacitance to 60V in 40 nanoseconds. Maybe you want that job. I
don\'t want that job. Particularly if they\'re from the Middle East
On 7/22/2020 10:01 AM, jlarkin@highlandsniptechnology.com wrote:
On Wed, 22 Jul 2020 02:54:38 -0400, bitrex <user@example.net> wrote:
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
Cool, 1964, obviously done on a fairly worn-out typewriter.
The Zetex parts are, to my knowledge, the only transistors
specifically designed to avalanche. They are apparently made on an
ancient Russian fab line, probably all diffused. Epitaxial transistors
seem to not avalanche much.
But given the Zetex monolopy, I\'m more interested in circuits and
physical PCB topologies, and especially actual experience.
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
Interesting, but I\'m not designing semiconductors, especially not with
germanium.
I don\'t think the math for silicon diffused transistors would be that
different vs. germanium, just different fudge-factors
The old HP and Tek sampling scopes seemed to use selected 2N-type
parts. Biased to maybe 60 volts or so, they could be triggered to make
maybe a 30 volt sampling spike under 100 ps wide. The 7S14 uses an
avalanche transistor to sample two channels and gets 2 GHz typical
bandwidth.
The ol\' 2D21 thyratrons, gas tube relay triggers for like jukeboxes and
stuff I guess, had very fast (ionization? de-ionization?) times for
their era. I dunno what the equivalent slew rate is exactly but the
rising edge on a relaxation sawtooth is fast enough that divided down
the usual jellybean opamps as unity-buffers with GBWs of 10s of MHz and
10 or 20 volt/usec slew rates can\'t keep up.
The old transistors roughly half-discharged the available voltage. HP
and Tek no doubt got selected parts from the makers; a random 2Nxxxx
would be unpredictable. The Zetex parts fire like an SCR, all the way
down to zero volts/shorted, and the SOT23s can dump 60 amps in around
a nanosecond. That\'s worth $6.
I saw a contract job posting where the client wanted circuit to charge a
400n capacitance to 60V in 40 nanoseconds. Maybe you want that job. I
don\'t want that job. Particularly if they\'re from the Middle East
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
On 7/21/2020 1:02 PM, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
\"in most junctions breakdown is due to secondary ionization which
results when minority carriers enter the reverse biased junction.
Because of the similarity to breakdown in gases this has been named
avalanche breakdown.\"
Here is a sprawling paper with lots of info about avalanche transistors:
https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4858&context=rtd
On page 8 an equation is given that shows the collector current above
the CE breakdown voltage, where Hfe is negative, and is in terms of an
emitter efficiency y, a transport factor B, and the avalanche
multiplication factor for electrons, M_n.
\"If an avalanche transistor is to be used as a bistable switch
the collector voltage during conduction should be made as low as
possible when compared to the collector voltage during the time the
transistor is turned off. cE(off) is limited by the breakdown voltage of
the collector junction, that collector voltage at which
M_n = (1/y*B)/(1 + Ib/Ic).
In order for this to occur at as low a value of M_n as possible the y*B
product should be as large as possible. This product cannot have a value
greater than 1, and it is at least 0.95 in any practical transistor, so
very little can be done to further control this quantity. The
alternative approach is to design the collector so that the required
value of M_n occurs at a lower collector voltage.\"
On 21/07/2020 18:02, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
At Ferranti in the 70\'s we used a stack of Ferranti/Zetex e-line
transistors ZTX 3xx or 4xx series as a Laser Q switch modulator. The
transistors had to be specially selected for breakdown
Similar to this ,but with a lot more transistors as the ZTX had a lower
breakdown. We abandoned it when we switched from KD*P TO lithium niobate
cells which needed a higher voltage.
https://www.osti.gov/servlets/purl/325425-ayLMLC/webviewable/
Brian
--
Brian
On 21/07/2020 18:02, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
At Ferranti in the 70\'s we used a stack of Ferranti/Zetex e-line
transistors ZTX 3xx or 4xx series as a Laser Q switch modulator. The
transistors had to be specially selected for breakdown
Similar to this ,but with a lot more transistors as the ZTX had a lower
breakdown. We abandoned it when we switched from KD*P TO lithium niobate
cells which needed a higher voltage.
https://www.osti.gov/servlets/purl/325425-ayLMLC/webviewable/
Brian
--
Brian