fast discrete PHEMT one-shot

Post by John Larkin
https://www.dropbox.com/scl/fi/agatzclr8pvr5470g6mc4/Phemt_One_Shot_1.jpg?rlkey=cwnx0qd7ajgnh8otf627x5lku&raw=1
Regular monostables are terribly slow. This one has low prop delay and
high rep-rate, if the sim is to be believed.
SAV541 is mostly specified as an RF part, but it's a dynamite switch.
I can post a link to the files if anybody wants to play with this. All
my values are first guesses, no math involved, and it works!
My SAV541 Spice model is a revision of Phil Hobbs' original.
Mini-Circuits is adamant that they will never provide Spice models, a
typical RF-bigot attitude.

With a low-resistance drain load like that, you don't care too much
about the low drain impedance of the pHEMT. The old Avago ones were
around 160 ohms iirc. The transconductance is high enough (400 mho or
something ridiculous like that) that you get gobs of voltage gain even so.

Really really crappy for followers though!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

John Larkin

2024-05-15 18:33:52 UTC

On Wed, 15 May 2024 14:22:36 -0400, Phil Hobbs

With a low-resistance drain load like that, you don't care too much
about the low drain impedance of the pHEMT. The old Avago ones were
around 160 ohms iirc. The transconductance is high enough (400 mho or
something ridiculous like that) that you get gobs of voltage gain even so.
Really really crappy for followers though!
Cheers
Phil Hobbs

My (our) Spice model

.MODEL SAV541a NMF(vto=0.08, Beta=0.6,
+ Lambda=0.07, Alpha=4 B=0.8, Pb=0.7,
+ Cgs=0.997E-12, Cgd=0.176E-12, Rd=0.084,
+ Rs=0.054, Kf=5e-11, Af=2, Is=1.5e-19)

doesn't include Cds. Maybe that's why I'm simulating 16 ps prop delay
from trig to Q+. I need to build one.

I have measured real-world stuff like Rds-on, gate diode curves,
actual drain breakdown voltage. Things get interesting past +1 on the
gate.

The RF boys seem to assume that the drain drives a tank, so peak drain
voltage swings to 2x "abs max".

Phil Hobbs

2024-05-16 00:00:56 UTC

With a low-resistance drain load like that, you don't care too much
about the low drain impedance of the pHEMT. The old Avago ones were
around 160 ohms iirc. The transconductance is high enough (400

millimho or

Post by Phil Hobbs
something ridiculous like that) that you get gobs of voltage gain even so.
Really really crappy for followers though!
Cheers
Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

John Larkin

2024-05-16 01:07:12 UTC

On Thu, 16 May 2024 00:00:56 -0000 (UTC), Phil Hobbs

With a low-resistance drain load like that, you don't care too much
about the low drain impedance of the pHEMT. The old Avago ones were
around 160 ohms iirc. The transconductance is high enough (400

millimho or

Rds-on is about 2 ohms with a half a volt or so on the gate.

Interestingly, they seem to keep turning on harder with insane gate
voltages, like +1 or so. Ig is about 16 mA, way past abs max, at 1
volt, but I'll just pulse it so it will be fine. Right?

Post by Phil Hobbs
something ridiculous like that) that you get gobs of voltage gain even so.
Really really crappy for followers though!

Tell me about that. My triggered 50 MHz colpitts oscillator squegged
at around 4 GHz. Tons of jitter.

I designed a new osc using a BUF602 and it's great.

piglet

2024-05-15 22:46:27 UTC

Yay! Eccles-Jordan ride again.

--
piglet

John Larkin

2024-05-16 01:15:34 UTC

On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet

Yay! Eccles-Jordan ride again.

1918!

I think that was a bistable. I don't know when the monostable was
invented.

People tend to roll eyes when I use one-shots in logic designs. I
can't see why.

Phil Hobbs

2024-05-16 02:14:49 UTC

Post by John Larkin
On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet

Yay! Eccles-Jordan ride again.

1918!
I think that was a bistable. I don't know when the monostable was
invented.
People tend to roll eyes when I use one-shots in logic designs. I
can't see why.

Probably because the classical TTL and CMOS multivibrator chips are so
horrible.

The CMOS versions of the 555 are about the best, which is amusing since
they’re the ones that get all the abuse.

My usual rule is that one-shots are fine if you can accommodate a factor of
3 uncertainty in the delay.

Joerg used to wrap feedback loops around them.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

Bill Sloman

2024-05-16 14:40:32 UTC

Post by John Larkin
On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet

Yay! Eccles-Jordan ride again.

1918!
I think that was a bistable. I don't know when the monostable was > invented.

https://en.wikipedia.org/wiki/Multivibrator

has a two quotes from 1942 one from 1943 and two from 1949 which make it
clear that monostable had been invented by then. It sees it as a cut
down bistable, so Eccles-Jordan is probably a good name.

Since the first multivibrator circuit, the astable multivibrator
oscillator, was invented by Henri Abraham and Eugene Bloch during World
War I, it probably isn't the right name.

https://apps.dtic.mil/sti/tr/pdf/AD0410225.pdf

is a 1963 Ph.D. on the bistable circuit.

Post by John Larkin
People tend to roll eyes when I use one-shots in logic designs. I
can't see why.

You can't trigger a one-shot immediately after it has been triggered,
and the pulse width you get can be reduced if you re-trigger it too soon
after it has generated it's pulse, when it hasn't entirely recovered.

Using a properly terminated delay line to set the output pulse width
could reduce this uncertainty, but I've never done it.

Ghiggino, K.P., Phillips, D., and Sloman, A.W. "Nanosecond pulse
stretcher",Journal of Physics E: Scientific Instruments, 12, 686-687 (1979).

just used two 5GHz wide-band transistors (BFT95) and was perfectly
horrible, but it did what Dave Phillips and Ken Ghiggino had wanted me
to give them, and Ken Ghiggino wrote it up rather badly, but I was able
to rework the short paper into a form that was publishable and looks
nice on Ken's CV.

The fact the laser pulses it was designed to detect arrived at a steady
20MHz meant that it's worst defect didn't matter.

--
Bill Sloman, Sydney

John Larkin

2024-05-16 16:46:16 UTC

Post by John Larkin
On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet

Yay! Eccles-Jordan ride again.

1918!
I think that was a bistable. I don't know when the monostable was > invented.

https://en.wikipedia.org/wiki/Multivibrator
has a two quotes from 1942 one from 1943 and two from 1949 which make it
clear that monostable had been invented by then. It sees it as a cut
down bistable, so Eccles-Jordan is probably a good name.
Since the first multivibrator circuit, the astable multivibrator
oscillator, was invented by Henri Abraham and Eugene Bloch during World
War I, it probably isn't the right name.
https://apps.dtic.mil/sti/tr/pdf/AD0410225.pdf
is a 1963 Ph.D. on the bistable circuit.

Post by John Larkin
People tend to roll eyes when I use one-shots in logic designs. I
can't see why.

The SN74123 retriggerable one-shot, and a Fairchild equivalent, are
over 50 years old.

And "it's" is not the possessive form. It's means "it is."

Edward Rawde

2024-05-16 20:41:15 UTC

Post by John Larkin
On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet

Yay! Eccles-Jordan ride again.

1918!
I think that was a bistable. I don't know when the monostable was > invented.

https://en.wikipedia.org/wiki/Multivibrator
has a two quotes from 1942 one from 1943 and two from 1949 which make it
clear that monostable had been invented by then. It sees it as a cut
down bistable, so Eccles-Jordan is probably a good name.
Since the first multivibrator circuit, the astable multivibrator
oscillator, was invented by Henri Abraham and Eugene Bloch during World
War I, it probably isn't the right name.
https://apps.dtic.mil/sti/tr/pdf/AD0410225.pdf
is a 1963 Ph.D. on the bistable circuit.

Post by John Larkin
People tend to roll eyes when I use one-shots in logic designs. I
can't see why.

The SN74123 retriggerable one-shot, and a Fairchild equivalent, are
over 50 years old.
And "it's" is not the possessive form. It's means "it is."

But it can also mean "it has" and who cares anyway.
I often find, when typing fast, that I used the wrong form when I re read my
sentence.
I even typed dentence then and had to change the d.

One-shots were frequently used in logic designs when gates were four per
package because designers still knew what they were doing with components
such as resistors, capacitors, inductors etc.
I'm sure some still do but not many.
50 years from now it will likely all be done by AD. (Artificial Designer).

John Larkin

2024-05-17 02:04:32 UTC

On Thu, 16 May 2024 16:41:15 -0400, "Edward Rawde"

Post by Edward Rawde

Post by John Larkin
On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet

Yay! Eccles-Jordan ride again.

1918!
I think that was a bistable. I don't know when the monostable was > invented.

https://en.wikipedia.org/wiki/Multivibrator
has a two quotes from 1942 one from 1943 and two from 1949 which make it
clear that monostable had been invented by then. It sees it as a cut
down bistable, so Eccles-Jordan is probably a good name.
Since the first multivibrator circuit, the astable multivibrator
oscillator, was invented by Henri Abraham and Eugene Bloch during World
War I, it probably isn't the right name.
https://apps.dtic.mil/sti/tr/pdf/AD0410225.pdf
is a 1963 Ph.D. on the bistable circuit.

Post by John Larkin
People tend to roll eyes when I use one-shots in logic designs. I
can't see why.

The SN74123 retriggerable one-shot, and a Fairchild equivalent, are
over 50 years old.
And "it's" is not the possessive form. It's means "it is."

But it can also mean "it has" and who cares anyway.
I often find, when typing fast, that I used the wrong form when I re read my
sentence.
I even typed dentence then and had to change the d.

You've got to admit that his pompous lecture, about all the inherent
defects of one-shots, was amusing.

I tweaked my phemt one-shot a bit, just for fun. I might even have a
use for it.

Loading Image...

One cool old circuit that predated ICs was the uni-shot, a single
transistor and three passives. It was used in model airplane r/c
transmitters. One of the three passives was a joystick pot.

Bill Sloman

2024-05-17 05:43:33 UTC

Post by John Larkin
On Thu, 16 May 2024 16:41:15 -0400, "Edward Rawde"

Post by Edward Rawde

Post by John Larkin
On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet

Yay! Eccles-Jordan ride again.

1918!
I think that was a bistable. I don't know when the monostable was > invented.

https://en.wikipedia.org/wiki/Multivibrator
has a two quotes from 1942 one from 1943 and two from 1949 which make it
clear that monostable had been invented by then. It sees it as a cut
down bistable, so Eccles-Jordan is probably a good name.
Since the first multivibrator circuit, the astable multivibrator
oscillator, was invented by Henri Abraham and Eugene Bloch during World
War I, it probably isn't the right name.
https://apps.dtic.mil/sti/tr/pdf/AD0410225.pdf
is a 1963 Ph.D. on the bistable circuit.

Post by John Larkin
People tend to roll eyes when I use one-shots in logic designs. I
can't see why.

The SN74123 retriggerable one-shot, and a Fairchild equivalent, are
over 50 years old.
And "it's" is not the possessive form. It's means "it is."

But it can also mean "it has" and who cares anyway.
I often find, when typing fast, that I used the wrong form when I re read my
sentence.
I even typed dentence then and had to change the d.

You've got to admit that his pompous lecture, about all the inherent
defects of one-shots, was amusing.

John Larkin objects to any post that doesn't flatter him. One that
points out that he didn't do his home work is even more objectionable.

Post by John Larkin
I tweaked my phemt one-shot a bit, just for fun. I might even have a
use for it.
https://www.dropbox.com/scl/fi/zoncsuiz2ifl30i1tw0cl/Phemt_One-shot_2.jpg?rlkey=z77hx5kkdpijmz5rs7ex63jq7&raw=1
One cool old circuit that predated ICs was the uni-shot, a single
transistor and three passives. It was used in model airplane r/c
transmitters. One of the three passives was a joystick pot.

Eccles-Jordan (more correctly Abraham-Bloch) used valves - they predate
transistors as well as integrated circuits.

--
Bill Sloman, Sydney

piglet

2024-05-17 22:11:08 UTC

Post by John Larkin
One cool old circuit that predated ICs was the uni-shot, a single
transistor and three passives. It was used in model airplane r/c
transmitters. One of the three passives was a joystick pot.

Uni-shot is unfamiliar to me, I called them “half-shots”. Cascaded as
required.

--
piglet

Bill Sloman

2024-05-17 05:37:13 UTC

Post by John Larkin
On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet

Yay! Eccles-Jordan ride again.

1918!
I think that was a bistable. I don't know when the monostable was > invented.

https://en.wikipedia.org/wiki/Multivibrator
has a two quotes from 1942 one from 1943 and two from 1949 which make it
clear that monostable had been invented by then. It sees it as a cut
down bistable, so Eccles-Jordan is probably a good name.
Since the first multivibrator circuit, the astable multivibrator
oscillator, was invented by Henri Abraham and Eugene Bloch during World
War I, it probably isn't the right name.
https://apps.dtic.mil/sti/tr/pdf/AD0410225.pdf
is a 1963 Ph.D. on the bistable circuit.

Post by John Larkin
People tend to roll eyes when I use one-shots in logic designs. I
can't see why.

The SN74123 retriggerable one-shot, and a Fairchild equivalent, are
over 50 years old.

But you don't get a new pulse when you retrigger a retriggerable
monostable - you just stretch the one you had already started.

Post by John Larkin
And "it's" is not the possessive form. It's means "it is."

I do know that but produce the mistake as a typo from time to time, as
you are well aware.

And you've snipped the rest of my post, without marking the snip.

--
Bill Sloman, Sydney

Bill Sloman

2024-05-18 05:58:09 UTC

Post by John Larkin
On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet