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
9-decade transimpedance amplifier
Started by ●June 26, 2019
Reply by ●June 26, 20192019-06-26
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-pWAwuuZlZLvlFArdHow 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
Reply by ●June 26, 20192019-06-26
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.
Reply by ●June 26, 20192019-06-26
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 >ZlZLvlFArdThank you, very intersting.. but you *are* switching feedback resistors ;-)
Reply by ●June 26, 20192019-06-26
John Larkin wrote...> > How about this? >https://www.dropbox.com/s/1gud5ftlsmnsqtx/Wide_Range_TIA.jpg?raw=1That 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
Reply by ●June 26, 20192019-06-26
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=0Fig 4x.31 are all three outputs "FS=100nA"?
Reply by ●June 26, 20192019-06-26
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
Reply by ●June 26, 20192019-06-26
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
Reply by ●June 26, 20192019-06-26
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
Reply by ●June 26, 20192019-06-26
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.
