9-decade transimpedance amplifier

[Winfield Hill]

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd


--
Thanks,
- Win

 

[John Larkin]

On 26 Jun 2019 09:48:33 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd

How about this?

https://www.dropbox.com/s/1gud5ftlsmnsqtx/Wide_Range_TIA.jpg?raw=1



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[bitrex]

On 6/26/19 12:48 PM, Winfield Hill wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd

If not every component in the circuit is going to have a designator
because they're irrelevant to the discussion that's OK but if only some
are labeled plz associate e.g. an R3 with a C3 if they are next to each
other, the text mentions R1 and I'm looking for it over by C1 and not
over by C3 where it is now.

do they mean the 1k? hmmm that doesn't seem right oh, okay R1 is
actually over there on the right.

 

[Winfield Hill]

bitrex wrote...

If not every component in the circuit is going to have
a designator because they're irrelevant to the discussion
that's OK but if only some are labeled plz associate
e.g. an R3 with a C3 if they are next to each other,
the text mentions R1 and I'm looking for it over by C1
and not over by C3 where it is now.

I'm sorry if the order threw you off, R1 is the
highest range and that must be R1. As you decide
to add ranges, you get R4 R5, etc. The C2 C3
caps are incidental, omit, most likely. So I
think C1 has to be the always-included cap. But
we can swap the C2 C3 designators.

Sheesh, I did discover a misleading error, in the
"Now for the trick:" paragraph, the active JFETs
are p-channel, Q4 and Q2, not n-channel. And the
Figure 4x.31 scaling error, that Tom pointed out.


--
Thanks,
- Win

 

[Winfield Hill]

Tom Gardner wrote...

Fig 4x.31 are all three outputs "FS=100nA"?

Thanks, Tom, it's nice to discover these
careless errors before it goes to press!


--
Thanks,
- Win

 

[Winfield Hill]

Jan Panteltje wrote...

Thank you, very intersting..
but you *are* switching feedback resistors ;-)

Well, not at the range changes, exactly.
As one starts using a lower-gain output,
the higher-gain one is still available.
Eventually, when you don't care about it
anymore, it gets shorted. I'm sorry, if
my "no-switching" rule prevented you from
discovering an answer. It's certainly not
gain switching as we've done it all along.


--
Thanks,
- Win

 

[Tom Gardner]

On 26/06/19 17:48, Winfield Hill wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

Fig 4x.31 are all three outputs "FS=100nA"?

 

[Winfield Hill]

John Larkin wrote...

How about this?
https://www.dropbox.com/s/1gud5ftlsmnsqtx/Wide_Range_TIA.jpg?raw=1

That could work, sort of. The beauty of the
Eckel circuit is the substantial range of its
overlapping simultaneous outputs, as you go
through range changes.

You won't be trying to digitize an opamp all
the way to its saturation, and wait for the
next stage to begin working.

If you have a very noisy signal, having two
amplifier signal versions, at different gains,
lets you process data from two channals and
get a clean result.

Note, it has a similar parts count: one opamp
per range, and JFET instead of a diode. It'd
be a good addition to your bag of tricks.

Also, Eckel's circuit can work through zero,
with bipolar input currents.


--
Thanks,
- Win

 

[Jan Panteltje]

On a sunny day (26 Jun 2019 09:48:33 -0700) it happened Winfield Hill
<winfieldhill@yahoo.com> wrote in <qf07l1023jb@drn.newsguy.com>:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%
2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuu
ZlZLvlFArd

Thank you, very intersting..
but you *are* switching feedback resistors ;-)

 

[Jan Panteltje]

On a sunny day (26 Jun 2019 11:06:06 -0700) it happened Winfield Hill
<winfieldhill@yahoo.com> wrote in <qf0c6e029bv@drn.newsguy.com>:

Jan Panteltje wrote...

Thank you, very intersting..
but you *are* switching feedback resistors ;-)

Well, not at the range changes, exactly.
As one starts using a lower-gain output,
the higher-gain one is still available.
Eventually, when you don't care about it
anymore, it gets shorted. I'm sorry, if
my "no-switching" rule prevented you from
discovering an answer. It's certainly not
gain switching as we've done it all along.

No, no problem, but I thought somebody else wanted to change resistor values?

<quote from 2012_Eckel,Sushkov_9-decade_RSI.pdf>
We have built a high dynamic range (nine decade) transimpedance ampli
The amplifier uses junction-gate field effect transistors (JFETs) to switch
^^^^^^^^
resistors in the feedback of a low input bias current operational amplifier.
^^^^^^^^^^^^^^^^^^^^^^^^^
<end quote>


My idea was a log amplifier...

It is a nice circuit, surprises me that the switching with simple JFETs works so well.
Thank you, will keep this, may come in handy one day.

 

[Winfield Hill]

Steve Wilson wrote...

Winfield Hill wrote:

I think you can download Stephen's RSI article here: ...

Easier download link:

http://www.bmo.physik.uni-muenchen.de/~riedle/Elektronik_I/KW103/2012
_Eckel,Sushkov_9-decade_RSI.pdf

It appears some people were paying attention, and
trying to get the word out, past the paywall.


--
Thanks,
- Win

 

[Steve Wilson]

Winfield Hill <winfieldhill@yahoo.com> wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUK
Ewjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.
uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9
-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd

Easier download link:

http://www.bmo.physik.uni-muenchen.de/~riedle/Elektronik_I/KW103/2012
_Eckel,Sushkov_9-decade_RSI.pdf

 

[George Herold]

On Wednesday, June 26, 2019 at 1:24:07 PM UTC-4, John Larkin wrote:

On 26 Jun 2019 09:48:33 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd


How about this?

https://www.dropbox.com/s/1gud5ftlsmnsqtx/Wide_Range_TIA.jpg?raw=1

Huh, So first I assume the higher gains, (bigger Rs) are on top..
behind the diodes. Then a question; how does the current 'know' which path
to take?

Oh, If I put the high range on the bottom, then when it can't handle any
more next one up takes over... Is that right? That's cute too!

George H.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[George Herold]

On Wednesday, June 26, 2019 at 12:48:43 PM UTC-4, Winfield Hill wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd


--
Thanks,
- Win

Fun Thanks.
George H.

 

[John Larkin]

On 26 Jun 2019 10:52:37 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

John Larkin wrote...

How about this?
https://www.dropbox.com/s/1gud5ftlsmnsqtx/Wide_Range_TIA.jpg?raw=1

That could work, sort of. The beauty of the
Eckel circuit is the substantial range of its
overlapping simultaneous outputs, as you go
through range changes.

You won't be trying to digitize an opamp all
the way to its saturation, and wait for the
next stage to begin working.

If you have a very noisy signal, having two
amplifier signal versions, at different gains,
lets you process data from two channals and
get a clean result.

Note, it has a similar parts count: one opamp
per range, and JFET instead of a diode. It'd
be a good addition to your bag of tricks.

Also, Eckel's circuit can work through zero,
with bipolar input currents.

Mine can work bipolar, with more diodes. But a photodiode deosn't need
bipolar.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Wed, 26 Jun 2019 12:19:35 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Wednesday, June 26, 2019 at 1:24:07 PM UTC-4, John Larkin wrote:
On 26 Jun 2019 09:48:33 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd


How about this?

https://www.dropbox.com/s/1gud5ftlsmnsqtx/Wide_Range_TIA.jpg?raw=1
Huh, So first I assume the higher gains, (bigger Rs) are on top..
behind the diodes. Then a question; how does the current 'know' which path
to take?

Oh, If I put the high range on the bottom, then when it can't handle any
more next one up takes over... Is that right? That's cute too!

George H.

Right, higher gain, big Rf, is on the bottom. When that stage rails,
the excess input current moves up to the next stage. The diode drop
produces a low-order error that is easily fudged away.

It only works right with a current-source input.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[piglet]

On 26/06/2019 5:48 pm, Winfield Hill wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd

Marvellous - thank you!

Jfets are nice because when fully depleted off there is no parasitic s-d
diode that curses gumdrop mosfets. But gumdrop mosfets are much cheaper
than jfets these days. I wonder if one could use series connected
source-source 2N7002 and s-s BSS84 to replace those jfets? Eight mosfets
could work out cheaper than four jfets? While gate leakage should be a
non-issue I don't know how s-d channel leakage compares?

piglet

 

[George Herold]

On Wednesday, June 26, 2019 at 4:06:48 PM UTC-4, John Larkin wrote:

On Wed, 26 Jun 2019 12:19:35 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Wednesday, June 26, 2019 at 1:24:07 PM UTC-4, John Larkin wrote:
On 26 Jun 2019 09:48:33 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd


How about this?

https://www.dropbox.com/s/1gud5ftlsmnsqtx/Wide_Range_TIA.jpg?raw=1
Huh, So first I assume the higher gains, (bigger Rs) are on top..
behind the diodes. Then a question; how does the current 'know' which path
to take?

Oh, If I put the high range on the bottom, then when it can't handle any
more next one up takes over... Is that right? That's cute too!

George H.

Right, higher gain, big Rf, is on the bottom. When that stage rails,
the excess input current moves up to the next stage. The diode drop
produces a low-order error that is easily fudged away.

It only works right with a current-source input.

Right PD biased up to at least -10V, or something.
We sell a PD with a 10 position switch, 1,3.3,10...
It's OK, when I tried to make it faster I found the switch
added ~5 pF of C. Otherwise I'm not sure what's wrong
with a gain switch. A lower capacitance switch would be nice.
Square posts with jumpers would be less than 5pF, but more of
a pain to change.

George H.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[George Herold]

On Wednesday, June 26, 2019 at 5:22:34 PM UTC-4, piglet wrote:

On 26/06/2019 5:48 pm, Winfield Hill wrote:
Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd




Marvellous - thank you!

Jfets are nice because when fully depleted off there is no parasitic s-d
diode that curses gumdrop mosfets. But gumdrop mosfets are much cheaper
than jfets these days. I wonder if one could use series connected
source-source 2N7002 and s-s BSS84 to replace those jfets? Eight mosfets
could work out cheaper than four jfets? While gate leakage should be a
non-issue I don't know how s-d channel leakage compares?

piglet

I was going to ask what about source-source fets, and found this,
https://electronics.stackexchange.com/questions/79028/understanding-two-mosfet-with-sources-connected

Is that right... just looking at pics not reading comments/ words.

George H.

 

[John Larkin]

On Wed, 26 Jun 2019 17:43:27 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Wednesday, June 26, 2019 at 4:06:48 PM UTC-4, John Larkin wrote:
On Wed, 26 Jun 2019 12:19:35 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Wednesday, June 26, 2019 at 1:24:07 PM UTC-4, John Larkin wrote:
On 26 Jun 2019 09:48:33 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

Here's a TIA circuit published in 2012, in RSI,
by Yale physicist, Stephen Eckel. “A high dynamic
range, linear response transimpedance amplifier.”

It's easy to implement, and super useful. The TIA
has multiple ranges, each with its own output, but
multiple ranges are active at once; there's no loss
of data as would happen switching range resistors.

Stephen and his co-authors found a simple, clever
trick to prevent input TIA opamp saturation, using
JFETs to successively short series-placed higher-
value range resistors for strong input currents.

They suggest a three-stage implementation, with a
300:1 ratio for each, but you can use many stages
(each one takes few extra parts), to obtain high
accuracy with a say 12-bit ADC. Also, a high
input-opamp Vos needn't degrade the dynamic range.

DropBox has a draft of our x-Chapters write-up:
https://www.dropbox.com/s/fs4edz7dqgwswoj/4x.3.7_Eckel_TIA.pdf?dl=0

I think you can download Stephen's RSI article here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=2ahUKEwjk6KvVwYfjAhVlRN8KHaMfD48QFjAHegQICRAC&url=http%3A%2F%2Fwww.bmo.physik.uni-muenchen.de%2F~riedle%2FElektronik_I%2FKW103%2F2012_Eckel%2CSushkov_9-decade_RSI.pdf&usg=AOvVaw3g9i6-pWAwuuZlZLvlFArd


How about this?

https://www.dropbox.com/s/1gud5ftlsmnsqtx/Wide_Range_TIA.jpg?raw=1
Huh, So first I assume the higher gains, (bigger Rs) are on top..
behind the diodes. Then a question; how does the current 'know' which path
to take?

Oh, If I put the high range on the bottom, then when it can't handle any
more next one up takes over... Is that right? That's cute too!

George H.

Right, higher gain, big Rf, is on the bottom. When that stage rails,
the excess input current moves up to the next stage. The diode drop
produces a low-order error that is easily fudged away.

It only works right with a current-source input.
Right PD biased up to at least -10V, or something.
We sell a PD with a 10 position switch, 1,3.3,10...
It's OK, when I tried to make it faster I found the switch
added ~5 pF of C. Otherwise I'm not sure what's wrong
with a gain switch. A lower capacitance switch would be nice.
Square posts with jumpers would be less than 5pF, but more of
a pain to change.

George H.

I did one photodiode amp using Phil's bootstrap cascode architecture,
except that I used two cascode NPNs, each going to its own opamp. By
seesawing the base voltages, I could select one or the other. That got
me two 10:1 gain ranges. I got another 10:1 downstream.

Great circuit, bad customer.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics