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Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
 
On 2020-07-21 19:02, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

I tried that, albeit stacking only two 2n3904 transistors and
self-triggered. Exceedingly noisy, in that no two pulses were
the same amplitude. I got 4ns, 70V pulses into 50 Ohms. I did
not pursue it any further.

Jeroen Belleman
 
On 2020-07-21 19:02, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

I tried that, albeit stacking only two 2n3904 transistors and
self-triggered. Exceedingly noisy, in that no two pulses were
the same amplitude. I got 4ns, 70V pulses into 50 Ohms. I did
not pursue it any further.

Jeroen Belleman
 
On 2020-07-21 19:02, jlarkin@highlandsniptechnology.com wrote:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

I tried that, albeit stacking only two 2n3904 transistors and
self-triggered. Exceedingly noisy, in that no two pulses were
the same amplitude. I got 4ns, 70V pulses into 50 Ohms. I did
not pursue it any further.

Jeroen Belleman
 
Am 21.07.20 um 19:02 schrieb jlarkin@highlandsniptechnology.com:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

Not a string, only 1 transistor fed from 350V.
The collector capacitor was a piece of coax, makes
a nice flat top. Cable Z should be low against the
50R in the emitter or one loses amplitude. Parallel
RG-188 is OK.

2N3904 is said to avalanche nicely.
We used something different, don\'t remember exactly what
for generating ultrasonic pulses with BaTitanate transducers.

Zetex/Diodes Inc. makes a transistor specified for
avalanching. Costs an arm & a leg.

We went later to an array of 32 300W amplifiers for a
beam steering phased array. Building the power stages
would have been a dream job for me as a ham, but I
had to do the phase & amplitude control. The transmitter
transistors were 4 each of the newest & best from
Motorola in Toulouse, nearly in Class A for a short time
for each shot.

Gerhard
 
Am 21.07.20 um 19:02 schrieb jlarkin@highlandsniptechnology.com:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

Not a string, only 1 transistor fed from 350V.
The collector capacitor was a piece of coax, makes
a nice flat top. Cable Z should be low against the
50R in the emitter or one loses amplitude. Parallel
RG-188 is OK.

2N3904 is said to avalanche nicely.
We used something different, don\'t remember exactly what
for generating ultrasonic pulses with BaTitanate transducers.

Zetex/Diodes Inc. makes a transistor specified for
avalanching. Costs an arm & a leg.

We went later to an array of 32 300W amplifiers for a
beam steering phased array. Building the power stages
would have been a dream job for me as a ham, but I
had to do the phase & amplitude control. The transmitter
transistors were 4 each of the newest & best from
Motorola in Toulouse, nearly in Class A for a short time
for each shot.

Gerhard
 
Am 21.07.20 um 19:02 schrieb jlarkin@highlandsniptechnology.com:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

Not a string, only 1 transistor fed from 350V.
The collector capacitor was a piece of coax, makes
a nice flat top. Cable Z should be low against the
50R in the emitter or one loses amplitude. Parallel
RG-188 is OK.

2N3904 is said to avalanche nicely.
We used something different, don\'t remember exactly what
for generating ultrasonic pulses with BaTitanate transducers.

Zetex/Diodes Inc. makes a transistor specified for
avalanching. Costs an arm & a leg.

We went later to an array of 32 300W amplifiers for a
beam steering phased array. Building the power stages
would have been a dream job for me as a ham, but I
had to do the phase & amplitude control. The transmitter
transistors were 4 each of the newest & best from
Motorola in Toulouse, nearly in Class A for a short time
for each shot.

Gerhard
 
On Tue, 21 Jul 2020 19:40:22 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 2020-07-21 19:02, jlarkin@highlandsniptechnology.com wrote:

Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?




I tried that, albeit stacking only two 2n3904 transistors and
self-triggered. Exceedingly noisy, in that no two pulses were
the same amplitude. I got 4ns, 70V pulses into 50 Ohms. I did
not pursue it any further.
Click to expand...

Sounds like the triggering was insufficiently powerful to ensure that
both 3904 units were fully on, simultaneously.

In power electronics, long serial strings of hocky-puck SCRs are used
to switch very large voltages (meaning a large factor larger than the
breakover voltage of any one SCR). While this can be done with
trigger transformers, it\'s far more common to use optically triggered
SCRs fed via optical fiber by an optical power splitter driven by a
single very healthy laser pulse generator.

I think this is also done with IGBTs. It ought to work with
phototransistors.

Joe Gwinn
 
On Tue, 21 Jul 2020 19:40:22 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 2020-07-21 19:02, jlarkin@highlandsniptechnology.com wrote:

Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?




I tried that, albeit stacking only two 2n3904 transistors and
self-triggered. Exceedingly noisy, in that no two pulses were
the same amplitude. I got 4ns, 70V pulses into 50 Ohms. I did
not pursue it any further.
Click to expand...

Sounds like the triggering was insufficiently powerful to ensure that
both 3904 units were fully on, simultaneously.

In power electronics, long serial strings of hocky-puck SCRs are used
to switch very large voltages (meaning a large factor larger than the
breakover voltage of any one SCR). While this can be done with
trigger transformers, it\'s far more common to use optically triggered
SCRs fed via optical fiber by an optical power splitter driven by a
single very healthy laser pulse generator.

I think this is also done with IGBTs. It ought to work with
phototransistors.

Joe Gwinn
 
On Tue, 21 Jul 2020 20:05:30 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 21.07.20 um 19:02 schrieb jlarkin@highlandsniptechnology.com:

Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?

Not a string, only 1 transistor fed from 350V.
The collector capacitor was a piece of coax, makes
a nice flat top. Cable Z should be low against the
50R in the emitter or one loses amplitude. Parallel
RG-188 is OK.

2N3904 is said to avalanche nicely.
We used something different, don\'t remember exactly what
for generating ultrasonic pulses with BaTitanate transducers.

Zetex/Diodes Inc. makes a transistor specified for
avalanching. Costs an arm & a leg.
Click to expand...

The Zetex parts are about $5 to 10 each, which isn\'t bad to
predictably make a sub-nanosecond, 350 volt pulse. They have some
appnotes about series connections for more voltage. I just wanted to
see if anyone here has done it.



We went later to an array of 32 300W amplifiers for a
beam steering phased array. Building the power stages
would have been a dream job for me as a ham, but I
had to do the phase & amplitude control. The transmitter
transistors were 4 each of the newest & best from
Motorola in Toulouse, nearly in Class A for a short time
for each shot.

Gerhard
Click to expand...
 
On Tue, 21 Jul 2020 20:05:30 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 21.07.20 um 19:02 schrieb jlarkin@highlandsniptechnology.com:

Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?

Not a string, only 1 transistor fed from 350V.
The collector capacitor was a piece of coax, makes
a nice flat top. Cable Z should be low against the
50R in the emitter or one loses amplitude. Parallel
RG-188 is OK.

2N3904 is said to avalanche nicely.
We used something different, don\'t remember exactly what
for generating ultrasonic pulses with BaTitanate transducers.

Zetex/Diodes Inc. makes a transistor specified for
avalanching. Costs an arm & a leg.
Click to expand...

The Zetex parts are about $5 to 10 each, which isn\'t bad to
predictably make a sub-nanosecond, 350 volt pulse. They have some
appnotes about series connections for more voltage. I just wanted to
see if anyone here has done it.



We went later to an array of 32 300W amplifiers for a
beam steering phased array. Building the power stages
would have been a dream job for me as a ham, but I
had to do the phase & amplitude control. The transmitter
transistors were 4 each of the newest & best from
Motorola in Toulouse, nearly in Class A for a short time
for each shot.

Gerhard
Click to expand...
 
On Tue, 21 Jul 2020 20:05:30 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 21.07.20 um 19:02 schrieb jlarkin@highlandsniptechnology.com:

Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?

Not a string, only 1 transistor fed from 350V.
The collector capacitor was a piece of coax, makes
a nice flat top. Cable Z should be low against the
50R in the emitter or one loses amplitude. Parallel
RG-188 is OK.

2N3904 is said to avalanche nicely.
We used something different, don\'t remember exactly what
for generating ultrasonic pulses with BaTitanate transducers.

Zetex/Diodes Inc. makes a transistor specified for
avalanching. Costs an arm & a leg.
Click to expand...

The Zetex parts are about $5 to 10 each, which isn\'t bad to
predictably make a sub-nanosecond, 350 volt pulse. They have some
appnotes about series connections for more voltage. I just wanted to
see if anyone here has done it.



We went later to an array of 32 300W amplifiers for a
beam steering phased array. Building the power stages
would have been a dream job for me as a ham, but I
had to do the phase & amplitude control. The transmitter
transistors were 4 each of the newest & best from
Motorola in Toulouse, nearly in Class A for a short time
for each shot.

Gerhard
Click to expand...
 
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

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

<jlarkin@highlandsniptechnology.com> wrote in message
news:eek:p7ehftp3c1ii2ehb8cvcc3e2duve21cfl@4ax.com...
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
Click to expand...
 
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

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

<jlarkin@highlandsniptechnology.com> wrote in message
news:eek:p7ehftp3c1ii2ehb8cvcc3e2duve21cfl@4ax.com...
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
Click to expand...
 
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

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

<jlarkin@highlandsniptechnology.com> wrote in message
news:eek:p7ehftp3c1ii2ehb8cvcc3e2duve21cfl@4ax.com...
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
Click to expand...
 
tirsdag den 21. juli 2020 kl. 19.02.23 UTC+2 skrev jla...@highlandsniptechnology.com:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

https://www.researchgate.net/figure/Complete-avalanche-pulse-generator-circuit_fig1_251842621

?
 
tirsdag den 21. juli 2020 kl. 19.02.23 UTC+2 skrev jla...@highlandsniptechnology.com:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

https://www.researchgate.net/figure/Complete-avalanche-pulse-generator-circuit_fig1_251842621

?
 
tirsdag den 21. juli 2020 kl. 19.02.23 UTC+2 skrev jla...@highlandsniptechnology.com:
Has anyone made high-voltage pulses from a series string of avalanche
transistors? Any wisdom?
Click to expand...

https://www.researchgate.net/figure/Complete-avalanche-pulse-generator-circuit_fig1_251842621

?
 
On Tue, 21 Jul 2020 19:06:27 -0500, \"Tim Williams\"
<tiwill@seventransistorlabs.com> wrote:

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
Click to expand...

What if the series avalanche transistors are spaced along a
transmission line? Gotta Spice that.

The Zetex SOT-23 parts can dump 60 amps!
 
On Tue, 21 Jul 2020 19:06:27 -0500, \"Tim Williams\"
<tiwill@seventransistorlabs.com> wrote:

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
Click to expand...

What if the series avalanche transistors are spaced along a
transmission line? Gotta Spice that.

The Zetex SOT-23 parts can dump 60 amps!
 
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