开云体育

Well I just simulated something I had not yet thought to do...... I simulated a Zener string.

Yeah, yeah it worked...... ha!

Largest Zener I could find in the model library was 36V so I strung enough of those to make about 890V nominal with a 3.3Meg dropper resistor. Its regulation is VERY flat only rose about 3V from 950V to 1200V input. That as good as my Penultimate Way-Good Cascode Shunt Regulator can do, and far less complex.

But guess what? over temperature it sucks big wind! +/-40V from -25 to 25 to 75degC! The Penultimate only varies about +/-3V over that temp range (overkill).

But the Good Enough Cascode Shunt Regulator, with its temperature compensation scheme, only varies less than +/-5V. Regulation varies less than 10V from about 950 to 1200V.

So the temp stability performance of the regulated 900+V is way-outstanding compared to a Zener string, in simulation!? AND it is adjustable!

rogerw

Peter,

Minor change, I noticed after I posted the note below that I had not specified the second BJT in the Darlington. The enclosed schematic is corrected and now the simulation predicts about dead-nuts on for the tempco of the output. Other than that, same comments as below. I think this is the best "good enough" cascoded shunt regulator.

rogerw

On 4/6/2022 10:40 AM, Roger Whatley via groups.io wrote:

Peter,Enclosed is a schematic of my suggestion below. That is an 8.2V Rohm Zener chosen for tempco to cancel the negative tempco of two Vbe's. It is slightly too positive in the result but quite "good enough." You willr just get much flatter regulation with the Darlington pair and that can be had in a single package.

Of course, depending on the Vcemax spec of your cascode MOSFET, you might have only one cascode instead of two..... That will not make a noticeable difference except to breakdown.

rogerw

On 4/6/2022 8:32 AM, Roger Whatley via groups.io wrote:

Peter,

I realize that circuit described below might be "good enough," but realize that making that one BJT a Darlington pair is a significant improvement to the regulation. You can even get the Darlington in one transistor package, of course, cheap.

As UnRegHV increases, the current in the BJT necessarily increases in order to regulate the loop. For every extra 0.1uA of extra base current required, the voltage drop in the feedback resistors (66M + 66M + 1M) goes up 0.1uA*(66M+66M+1M) = 13.3V and thus regulation suffers. The BJT current easliy goes from less than 10uA to over 200uA, thus the base current might go up by a worst-case of as much as 1uA, giving a 133V change in the output. So that is the motivation for the Darlington.

(In case anyone wonders, why not an FET instead of a BJT, that WAS the original circuit and it suffers worse circuit errors.....)

The next big error is that as the BJT current increases with UnRegHV increases, so does Vbe and Vz increase. Those are the motivations for subsequent circuit complications and resulting in the Penultimate Way-Improved version..... it is overkill, I know, to the requirement, but by simulating those improvements I gain insights as to just what the remaining errors were. And it was fun!

My take is that your present circuit, but with a Darlington Pair, will be "good enough" and if it were a purpose-built Darlington in one three-lead package, no more expensive or even board-space than a single BJT.

Of course, a single Zener voltage may be chosen to match the negative tempco of two Vbe's. Again, no extra expense or board space. (Off the top of my head, I am thinking about 8V Zener for +4mV/degC?)

rogerw

On 4/4/2022 10:33 PM, peter via groups.io wrote:

Roger:
?back to the circuit you posted in message #300
Simple cascode, with only 1 npn tr + 2 mosfets.
Since I found the 2SK3265, I removed the 2nd mosfet so its very basic circuit.
66Meg, two 1 Meg, 100k+ 2.2M trimmer , 5.1V zener, 2SK3265, 2SC3311
Set trimmer for 900V, Vary input from 950~ 1150, output only varied 5V or less.
Heated the circuit with a hair dryer, got it up from 25C to about 60C, voltage rose may be 5 or 6 volts. Good enough for me!
Time to make it small enough to stuff inside my CDV-700 !
It on the LHS of the attached jpg, circuit in message #300 is on the RHS
P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

Virus-free.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

开云体育

Well I just simulated something I had not yet thought to do...... I simulated a Zener string.

Yeah, it worked...... ha!

Largest Zener I could find in the model library was 36V so I strung enough of those to make about 890V nominal with a 3.3Meg dropper resistor. Its regulation is very flat only rose about 3V from 1000V to 1200V input. That as good as my Penultimate Way-Good Cascode Shunt Regulator can do, and far less complex.

But guess what? over temperature it sucks big wind! +/-40V from -25 to 25 to 75degC! The Penultimate only varies about +/-3V over that temp range (overkill).

But the Good Enough Cascode Shunt Regulator, with its temperature compensation scheme, only varies less tha +/-5V. Regulation varies less than 10V from the knee to 950 to 1200V

Peter,

Minor change, I noticed after I posted the note below that I had not specified the second BJT in the Darlington. The enclosed schematic is corrected and now the simulation predicts about dead-nuts on for the tempco of the output. Other than that, same comments as below. I think this is the best "good enough" cascoded shunt regulator.

rogerw

On 4/6/2022 10:40 AM, Roger Whatley via groups.io wrote:

Peter,Enclosed is a schematic of my suggestion below. That is an 8.2V Rohm Zener chosen for tempco to cancel the negative tempco of two Vbe's. It is slightly too positive in the result but quite "good enough." You willr just get much flatter regulation with the Darlington pair and that can be had in a single package.

Of course, depending on the Vcemax spec of your cascode MOSFET, you might have only one cascode instead of two..... That will not make a noticeable difference except to breakdown.

rogerw

On 4/6/2022 8:32 AM, Roger Whatley via groups.io wrote:

Peter,

I realize that circuit described below might be "good enough," but realize that making that one BJT a Darlington pair is a significant improvement to the regulation. You can even get the Darlington in one transistor package, of course, cheap.

As UnRegHV increases, the current in the BJT necessarily increases in order to regulate the loop. For every extra 0.1uA of extra base current required, the voltage drop in the feedback resistors (66M + 66M + 1M) goes up 0.1uA*(66M+66M+1M) = 13.3V and thus regulation suffers. The BJT current easliy goes from less than 10uA to over 200uA, thus the base current might go up by a worst-case of as much as 1uA, giving a 133V change in the output. So that is the motivation for the Darlington.

(In case anyone wonders, why not an FET instead of a BJT, that WAS the original circuit and it suffers worse circuit errors.....)

The next big error is that as the BJT current increases with UnRegHV increases, so does Vbe and Vz increase. Those are the motivations for subsequent circuit complications and resulting in the Penultimate Way-Improved version..... it is overkill, I know, to the requirement, but by simulating those improvements I gain insights as to just what the remaining errors were. And it was fun!

My take is that your present circuit, but with a Darlington Pair, will be "good enough" and if it were a purpose-built Darlington in one three-lead package, no more expensive or even board-space than a single BJT.

Of course, a single Zener voltage may be chosen to match the negative tempco of two Vbe's. Again, no extra expense or board space. (Off the top of my head, I am thinking about 8V Zener for +4mV/degC?)

rogerw

On 4/4/2022 10:33 PM, peter via groups.io wrote:

Roger:
?back to the circuit you posted in message #300
Simple cascode, with only 1 npn tr + 2 mosfets.
Since I found the 2SK3265, I removed the 2nd mosfet so its very basic circuit.
66Meg, two 1 Meg, 100k+ 2.2M trimmer , 5.1V zener, 2SK3265, 2SC3311
Set trimmer for 900V, Vary input from 950~ 1150, output only varied 5V or less.
Heated the circuit with a hair dryer, got it up from 25C to about 60C, voltage rose may be 5 or 6 volts. Good enough for me!
Time to make it small enough to stuff inside my CDV-700 !
It on the LHS of the attached jpg, circuit in message #300 is on the RHS
P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

Virus-free.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

开云体育

Let me wait and see, I have some other things I would like to drive to completion.

rogerw

or are you saying that you send something to me for testing? That's fine too.

No problem.

Geo

---

From: "geoelectronics at rallstech.net" <GEOelectronics@...>
To: "CDV700CLUB" <[email protected]>
Sent: Wednesday, April 6, 2022 8:06:52 PM
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.

Roger, a loaner can usually be arranged for a worthy project like this. Let's talk offlist

GEOelectronics@...

Geo

---

From: "Roger Whatley" <rogwhat53@...>
To: "CDV700CLUB" <[email protected]>
Sent: Wednesday, April 6, 2022 7:07:20 PM
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.

No. I am stone-age engineer and will first use a protoboard, then if I build it I will use a perfboard. That's enough for me, I am not manufacturing the things.

However, I also do not have a HV supply I can sweep for testing the regulation either, though I do that in the simulation study for soundness of the design.

And in practice, the regulation kinda does not matter past a point, in the kind of application I have in mind. The unit to unit value of both UnRegHV voltage AND current limit would vary, but the circuit contains a potentiometer to zero out that and component tolerances. Once an adjustment is made the other tolerances don't change (except temp and aging). You only need enough regulation so that the tolerance on THAT error is meeting spec.

Now, I don't have an example of all the kinds of detectors one might want to use this on, like PMT detectors, but I am thinking mainly of 400V to 1000V or so bias of different GM tubes.

However, I do hear that YOU do have a variable HV supply..... I am ordering components for a build. Let me see what happens first..... I don't want to make promises yet, but I might send you some HV components to build a prototype and to test.

rogerw

On 4/6/2022 6:13 PM, Geo Dowell wrote:

Roger, when this gets beta tested, can you do an eagle cad or some other 2 side pth PCB CAD for SMD?

Geo

----- Original Message -----
From: Roger Whatley <rogwhat53@...>
To: [email protected]
Sent: Wed, 06 Apr 2022 11:53:04 -0400 (EDT)
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.

Peter,

Minor change, I noticed after I posted the
note below that I had not specified the second BJT in the
Darlington. The enclosed schematic is corrected and now the
simulation predicts about dead-nuts on for the tempco of the
output. Other than that, same comments as below. I think this is
the best "good enough" cascoded shunt regulator.

rogerw

On 4/6/2022 10:40 AM, Roger Whatley via
groups.io wrote:

Peter,Enclosed is a schematic of my
suggestion below. That is an 8.2V Rohm Zener chosen for tempco
to cancel the negative tempco of two Vbe's. It is slightly too
positive in the result but quite "good enough." You willr just
get much flatter regulation with the Darlington pair and that
can be had in a single package.

Of course, depending on the Vcemax spec of
your cascode MOSFET, you might have only one cascode instead
of two..... That will not make a noticeable difference except
to breakdown.

rogerw

On 4/6/2022 8:32 AM, Roger Whatley
via groups.io wrote:

Peter,

I realize that circuit described below
might be "good enough," but realize that making that one BJT
a Darlington pair is a significant improvement to the
regulation. You can even get the Darlington in one
transistor package, of course, cheap.

As UnRegHV increases, the current in the
BJT necessarily increases in order to regulate the loop. For
every extra 0.1uA of extra base current required, the
voltage drop in the feedback resistors (66M + 66M + 1M) goes
up 0.1uA*(66M+66M+1M) = 13.3V and thus regulation suffers.
The BJT current easliy goes from less than 10uA to over
200uA, thus the base current might go up by a worst-case of
as much as 1uA, giving a 133V change in the output. So that
is the motivation for the Darlington.

(In case anyone wonders, why not an FET
instead of a BJT, that WAS the original circuit and it
suffers worse circuit errors.....)

The next big error is that as the BJT
current increases with UnRegHV increases, so does Vbe and Vz
increase. Those are the motivations for subsequent circuit
complications and resulting in the Penultimate Way-Improved
version..... it is overkill, I know, to the requirement, but
by simulating those improvements I gain insights as to just
what the remaining errors were. And it was fun!

My take is that your present circuit, but
with a Darlington Pair, will be "good enough" and if it were
a purpose-built Darlington in one three-lead package, no
more expensive or even board-space than a single BJT.

Of course, a single Zener voltage may be
chosen to match the negative tempco of two Vbe's. Again, no
extra expense or board space. (Off the top of my head, I am
thinking about 8V Zener for +4mV/degC?)

rogerw

On 4/4/2022 10:33 PM, peter via
groups.io wrote:

Roger:

?back to the circuit you posted in message #300

Simple cascode, with only 1 npn tr + 2 mosfets.

Since I found the 2SK3265, I removed the 2nd mosfet so its
very basic circuit.

66Meg, two 1 Meg, 100k+ 2.2M trimmer , 5.1V zener, 2SK3265,
2SC3311

Set trimmer for 900V, Vary input from 950~ 1150, output only
varied 5V or less.

Heated the circuit with a hair dryer, got it up from 25C to
about 60C, voltage rose may be 5 or 6 volts. Good enough for
me!

Time to make it small enough to stuff inside my CDV-700 !

It on the LHS of the attached jpg, circuit in message #300 is
on the RHS

P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

Virus-free.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

开云体育

No. I am stone-age engineer and will first use a protoboard, then if I build it I will use a perfboard. That's enough for me, I am not manufacturing the things.

However, I also do not have a HV supply I can sweep for testing the regulation either, though I do that in the simulation study for soundness of the design.

And in practice, the regulation kinda does not matter past a point, in the kind of application I have in mind. The unit to unit value of both UnRegHV voltage AND current limit would vary, but the circuit contains a potentiometer to zero out that and component tolerances. Once an adjustment is made the other tolerances don't change (except temp and aging). You only need enough regulation so that the tolerance on THAT error is meeting spec.

Now, I don't have an example of all the kinds of detectors one might want to use this on, like PMT detectors, but I am thinking mainly of 400V to 1000V or so bias of different GM tubes.

However, I do hear that YOU do have a variable HV supply..... I am ordering components for a build. Let me see what happens first..... I don't want to make promises yet, but I might send you some HV components to build a prototype and to test.

rogerw

Roger, when this gets beta tested, can you do an eagle cad or some other 2 side pth PCB CAD for SMD?

Geo

----- Original Message -----
From: Roger Whatley <rogwhat53@...>
To: [email protected]
Sent: Wed, 06 Apr 2022 11:53:04 -0400 (EDT)
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.

Peter,

Minor change, I noticed after I posted the
note below that I had not specified the second BJT in the
Darlington. The enclosed schematic is corrected and now the
simulation predicts about dead-nuts on for the tempco of the
output. Other than that, same comments as below. I think this is
the best "good enough" cascoded shunt regulator.

rogerw

On 4/6/2022 10:40 AM, Roger Whatley via
groups.io wrote:

Peter,Enclosed is a schematic of my
suggestion below. That is an 8.2V Rohm Zener chosen for tempco
to cancel the negative tempco of two Vbe's. It is slightly too
positive in the result but quite "good enough." You willr just
get much flatter regulation with the Darlington pair and that
can be had in a single package.

Of course, depending on the Vcemax spec of
your cascode MOSFET, you might have only one cascode instead
of two..... That will not make a noticeable difference except
to breakdown.

rogerw

On 4/6/2022 8:32 AM, Roger Whatley
via groups.io wrote:

Peter,

I realize that circuit described below
might be "good enough," but realize that making that one BJT
a Darlington pair is a significant improvement to the
regulation. You can even get the Darlington in one
transistor package, of course, cheap.

As UnRegHV increases, the current in the
BJT necessarily increases in order to regulate the loop. For
every extra 0.1uA of extra base current required, the
voltage drop in the feedback resistors (66M + 66M + 1M) goes
up 0.1uA*(66M+66M+1M) = 13.3V and thus regulation suffers.
The BJT current easliy goes from less than 10uA to over
200uA, thus the base current might go up by a worst-case of
as much as 1uA, giving a 133V change in the output. So that
is the motivation for the Darlington.

(In case anyone wonders, why not an FET
instead of a BJT, that WAS the original circuit and it
suffers worse circuit errors.....)

The next big error is that as the BJT
current increases with UnRegHV increases, so does Vbe and Vz
increase. Those are the motivations for subsequent circuit
complications and resulting in the Penultimate Way-Improved
version..... it is overkill, I know, to the requirement, but
by simulating those improvements I gain insights as to just
what the remaining errors were. And it was fun!

My take is that your present circuit, but
with a Darlington Pair, will be "good enough" and if it were
a purpose-built Darlington in one three-lead package, no
more expensive or even board-space than a single BJT.

Of course, a single Zener voltage may be
chosen to match the negative tempco of two Vbe's. Again, no
extra expense or board space. (Off the top of my head, I am
thinking about 8V Zener for +4mV/degC?)

rogerw

On 4/4/2022 10:33 PM, peter via
groups.io wrote:

Roger:

?back to the circuit you posted in message #300

Simple cascode, with only 1 npn tr + 2 mosfets.

Since I found the 2SK3265, I removed the 2nd mosfet so its
very basic circuit.

66Meg, two 1 Meg, 100k+ 2.2M trimmer , 5.1V zener, 2SK3265,
2SC3311

Set trimmer for 900V, Vary input from 950~ 1150, output only
varied 5V or less.

Heated the circuit with a hair dryer, got it up from 25C to
about 60C, voltage rose may be 5 or 6 volts. Good enough for
me!

Time to make it small enough to stuff inside my CDV-700 !

It on the LHS of the attached jpg, circuit in message #300 is
on the RHS

P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

Virus-free.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

开云体育

Peter,

Minor change, I noticed after I posted the note below that I had not specified the second BJT in the Darlington. The enclosed schematic is corrected and now the simulation predicts about dead-nuts on for the tempco of the output. Other than that, same comments as below. I think this is the best "good enough" cascoded shunt regulator.

rogerw

Peter,Enclosed is a schematic of my suggestion below. That is an 8.2V Rohm Zener chosen for tempco to cancel the negative tempco of two Vbe's. It is slightly too positive in the result but quite "good enough." You willr just get much flatter regulation with the Darlington pair and that can be had in a single package.

Of course, depending on the Vcemax spec of your cascode MOSFET, you might have only one cascode instead of two..... That will not make a noticeable difference except to breakdown.

rogerw

On 4/6/2022 8:32 AM, Roger Whatley via groups.io wrote:

Peter,

I realize that circuit described below might be "good enough," but realize that making that one BJT a Darlington pair is a significant improvement to the regulation. You can even get the Darlington in one transistor package, of course, cheap.

As UnRegHV increases, the current in the BJT necessarily increases in order to regulate the loop. For every extra 0.1uA of extra base current required, the voltage drop in the feedback resistors (66M + 66M + 1M) goes up 0.1uA*(66M+66M+1M) = 13.3V and thus regulation suffers. The BJT current easliy goes from less than 10uA to over 200uA, thus the base current might go up by a worst-case of as much as 1uA, giving a 133V change in the output. So that is the motivation for the Darlington.

(In case anyone wonders, why not an FET instead of a BJT, that WAS the original circuit and it suffers worse circuit errors.....)

The next big error is that as the BJT current increases with UnRegHV increases, so does Vbe and Vz increase. Those are the motivations for subsequent circuit complications and resulting in the Penultimate Way-Improved version..... it is overkill, I know, to the requirement, but by simulating those improvements I gain insights as to just what the remaining errors were. And it was fun!

My take is that your present circuit, but with a Darlington Pair, will be "good enough" and if it were a purpose-built Darlington in one three-lead package, no more expensive or even board-space than a single BJT.

Of course, a single Zener voltage may be chosen to match the negative tempco of two Vbe's. Again, no extra expense or board space. (Off the top of my head, I am thinking about 8V Zener for +4mV/degC?)

rogerw

On 4/4/2022 10:33 PM, peter via groups.io wrote:

Roger:
?back to the circuit you posted in message #300
Simple cascode, with only 1 npn tr + 2 mosfets.
Since I found the 2SK3265, I removed the 2nd mosfet so its very basic circuit.
66Meg, two 1 Meg, 100k+ 2.2M trimmer , 5.1V zener, 2SK3265, 2SC3311
Set trimmer for 900V, Vary input from 950~ 1150, output only varied 5V or less.
Heated the circuit with a hair dryer, got it up from 25C to about 60C, voltage rose may be 5 or 6 volts. Good enough for me!
Time to make it small enough to stuff inside my CDV-700 !
It on the LHS of the attached jpg, circuit in message #300 is on the RHS
P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

Virus-free.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

开云体育

Peter,Enclosed is a schematic of my suggestion below. That is an 8.2V Rohm Zener chosen for tempco to cancel the negative tempco of two Vbe's. It is slightly too positive in the result but quite "good enough." You willr just get much flatter regulation with the Darlington pair and that can be had in a single package.

Of course, depending on the Vcemax spec of your cascode MOSFET, you might have only one cascode instead of two..... That will not make a noticeable difference except to breakdown.

rogerw

Peter,

I realize that circuit described below might be "good enough," but realize that making that one BJT a Darlington pair is a significant improvement to the regulation. You can even get the Darlington in one transistor package, of course, cheap.

As UnRegHV increases, the current in the BJT necessarily increases in order to regulate the loop. For every extra 0.1uA of extra base current required, the voltage drop in the feedback resistors (66M + 66M + 1M) goes up 0.1uA*(66M+66M+1M) = 13.3V and thus regulation suffers. The BJT current easliy goes from less than 10uA to over 200uA, thus the base current might go up by a worst-case of as much as 1uA, giving a 133V change in the output. So that is the motivation for the Darlington.

(In case anyone wonders, why not an FET instead of a BJT, that WAS the original circuit and it suffers worse circuit errors.....)

The next big error is that as the BJT current increases with UnRegHV increases, so does Vbe and Vz increase. Those are the motivations for subsequent circuit complications and resulting in the Penultimate Way-Improved version..... it is overkill, I know, to the requirement, but by simulating those improvements I gain insights as to just what the remaining errors were. And it was fun!

My take is that your present circuit, but with a Darlington Pair, will be "good enough" and if it were a purpose-built Darlington in one three-lead package, no more expensive or even board-space than a single BJT.

Of course, a single Zener voltage may be chosen to match the negative tempco of two Vbe's. Again, no extra expense or board space. (Off the top of my head, I am thinking about 8V Zener for +4mV/degC?)

rogerw

On 4/4/2022 10:33 PM, peter via groups.io wrote:

Roger:
?back to the circuit you posted in message #300
Simple cascode, with only 1 npn tr + 2 mosfets.
Since I found the 2SK3265, I removed the 2nd mosfet so its very basic circuit.
66Meg, two 1 Meg, 100k+ 2.2M trimmer , 5.1V zener, 2SK3265, 2SC3311
Set trimmer for 900V, Vary input from 950~ 1150, output only varied 5V or less.
Heated the circuit with a hair dryer, got it up from 25C to about 60C, voltage rose may be 5 or 6 volts. Good enough for me!
Time to make it small enough to stuff inside my CDV-700 !
It on the LHS of the attached jpg, circuit in message #300 is on the RHS
P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

Virus-free.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

开云体育

Ha Ha!

I will put all that in my Write Only Memory (WOM) for posterity!

rogerw

" ps - is Ne'er Dowell one of those Scottish clans in the Old World?? :-)"

Aye, the highlands! The neighbor?here in MO?raises red-haired Highlander cattle, reminds me 'o? home...

The only problem with living in the colonies is getting confused with public toilets. I'm a LADie right? Why shouldn't I use the Ladie's WC? Speaking of which, why are there so many Lasies in there?

Ne'er? Mac Doubhgaill? ? ?errr....Dowell

---

From: "Roger Whatley" <rogwhat53@...>
To: "CDV700CLUB" <[email protected]>
Sent: Wednesday, April 6, 2022 8:06:59 AM
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.IF th

My all-time favorite is the Write-only Memory chip.

rogerw

ps - is Ne'er Dowell one of those Scottish clans in the Old World?? :-)

On 4/6/2022 7:19 AM, Geo Dowell wrote:

Hi Roger,

If you like low power semiconductors, resistors, capacitors, let me send you a drawer full of zero drain, zero drift, zero distortion, ultimately stable as a rock, transistors, diodes, and ICs.

.

Choose from neither-nor gates, write only memory, core-amnesia, no-flip-/all-flop ICs. all-in-non-out registers, zero-gain opamps,? infinite Ohm resistors, low-Ohm capacitors, All components are smoke free, I know because I let their smoke out already..

Ne'er Dowell

---

From: "Roger Whatley" <rogwhat53@...>
To: "CDV700CLUB" <[email protected]>
Sent: Tuesday, April 5, 2022 8:26:03 PM
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.IF th

a 2uA opamp...... wow.

rogerw

On 4/5/2022 7:00 PM, Geo Dowell wrote:

not a problem P. Just curious.

Already got more projects than space-time

Well, 1 ma min isn't going to do me any good with 1kV or 2kV bias supplies.. Back to the ol' op-amp + 1G resistor.

Geo

"peter via groups.io" <epkoncept@...>
To: "CDV700CLUB" <[email protected]>
Sent: Tuesday, April 5, 2022 6:50:14 PM
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.IF th

Geo:
?Sorry I don't remember the part numbers. I saw an announcement by Microchip a while ago, but I can't find it, must have been vapor.
TI has a TL783 ( 125V) but its a series and not a shunt regulator. Sorry
P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

Virus-free.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

开云体育

Peter,

I realize that circuit described below might be "good enough," but realize that making that one BJT a Darlington pair is a significant improvement to the regulation. You can even get the Darlington in one transistor package, of course, cheap.

As UnRegHV increases, the current in the BJT necessarily increases in order to regulate the loop. For every extra 0.1uA of extra base current required, the voltage drop in the feedback resistors (66M + 66M + 1M) goes up 0.1uA*(66M+66M+1M) = 13.3V and thus regulation suffers. The BJT current easliy goes from less than 10uA to over 200uA, thus the base current might go up by a worst-case of as much as 1uA, giving a 133V change in the output. So that is the motivation for the Darlington.

(In case anyone wonders, why not an FET instead of a BJT, that WAS the original circuit and it suffers worse circuit errors.....)

The next big error is that as the BJT current increases with UnRegHV increases, so does Vbe and Vz increase. Those are the motivations for subsequent circuit complications and resulting in the Penultimate Way-Improved version..... it is overkill, I know, to the requirement, but by simulating those improvements I gain insights as to just what the remaining errors were. And it was fun!

My take is that your present circuit, but with a Darlington Pair, will be "good enough" and if it were a purpose-built Darlington in one three-lead package, no more expensive or even board-space than a single BJT.

Of course, a single Zener voltage may be chosen to match the negative tempco of two Vbe's. Again, no extra expense or board space. (Off the top of my head, I am thinking about 8V Zener for +4mV/degC?)

rogerw

Roger:
?back to the circuit you posted in message #300
Simple cascode, with only 1 npn tr + 2 mosfets.
Since I found the 2SK3265, I removed the 2nd mosfet so its very basic circuit.
66Meg, two 1 Meg, 100k+ 2.2M trimmer , 5.1V zener, 2SK3265, 2SC3311
Set trimmer for 900V, Vary input from 950~ 1150, output only varied 5V or less.
Heated the circuit with a hair dryer, got it up from 25C to about 60C, voltage rose may be 5 or 6 volts. Good enough for me!
Time to make it small enough to stuff inside my CDV-700 !
It on the LHS of the attached jpg, circuit in message #300 is on the RHS
P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

开云体育

My all-time favorite is the Write-only Memory chip.

rogerw

ps - is Ne'er Dowell one of those Scottish clans in the Old World?? :-)

Hi Roger,

If you like low power semiconductors, resistors, capacitors, let me send you a drawer full of zero drain, zero drift, zero distortion, ultimately stable as a rock, transistors, diodes, and ICs.

.

Choose from neither-nor gates, write only memory, core-amnesia, no-flip-/all-flop ICs. all-in-non-out registers, zero-gain opamps,? infinite Ohm resistors, low-Ohm capacitors, All components are smoke free, I know because I let their smoke out already..

Ne'er Dowell

---

From: "Roger Whatley" <rogwhat53@...>
To: "CDV700CLUB" <[email protected]>
Sent: Tuesday, April 5, 2022 8:26:03 PM
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.IF th

a 2uA opamp...... wow.

rogerw

On 4/5/2022 7:00 PM, Geo Dowell wrote:

not a problem P. Just curious.

Already got more projects than space-time

Well, 1 ma min isn't going to do me any good with 1kV or 2kV bias supplies.. Back to the ol' op-amp + 1G resistor.

Geo

"peter via groups.io" <epkoncept@...>
To: "CDV700CLUB" <[email protected]>
Sent: Tuesday, April 5, 2022 6:50:14 PM
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.IF th

Geo:
?Sorry I don't remember the part numbers. I saw an announcement by Microchip a while ago, but I can't find it, must have been vapor.
TI has a TL783 ( 125V) but its a series and not a shunt regulator. Sorry
P

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.

Virus-free.

-- 
rogerw
On the Catclaw
ΜΟΛΩΝ ΛΑΒΕ

The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.