Here's another elegant design and application of LM10 from 1982 NSC appnote.
0 to 15PSI pressure measurement using V-F circuit powered from 1.5V and with total current drain of about 1mA.
The internals of the LM10, and analog ics in general comes from an appreciation of what can be done with transistors that reside on the same substrate. It is a different circuit concept, quite different from the biasing schemes that are necessary with discrete design. Widlar understood bipolar transistors backwards and upside down and took it to the limit in the low voltage design of the LM10. It was one thing to make a 1.2 V bandgap reference, but it took an extra measure of insight to turn that upside down and make a 0.2 V reference that could work and be accurate on a 1.1 V power supply, so close to the bandgap voltage of silicon.
Another writer back in the day was Walt Jung. I totally dog-eared my copy of the IC Array Cookbook. Its was a great introduction to the unique type of analog circuit design possible when you have matched transistors. Walt was engineer and technical writer at Analog Devices, and the first editor of the Linear Tech magazine. His Op-Amp Cookbook, and Audio Circuits Cookbook and others in that series were a great training ground, now all out of print I think.
Yes, Jung, Don Lancaster's inspiring thoughts, folks from Burr-Brown, but also popular booklets from Forest M.Mimms III teaching his daughter circuit basics while popularizing hands-on electronics to others... good stories to remember.
Here's Jim Williams designs around LM10 in LT Appnote from 1985 (he uses LM10 there as one of the only 2 IC's available to work those wonders at 1.5V at that time). Notice how nonchalantly and almost by-the-way'ish he brings to us "transistor operating in inverted mode'. Say what? Only IEEE papers discussed it at all and there he was using it here and there... I was taught that the transistor in inverted mode goes into an avalanche mode, i.e. dangerous zone and is ready to go pufffffff...
He show me how very little did I know of low battery circuits. Add to that the LT1615 micropower DC-DC http://www.linear.com/product/LT1615 (probably of his design as well) and I might 'never' throw away any AA or AAA :-)
The use of the inverted transistor is very interesting. The reason for it is, as stated toward the end of the article, is that the saturation voltage in inverted mode is near 1 mV, whereas in normal mode with the silicon transistor, Vce at saturation is nearly 100mV. I didn't know that about inverted mode (filing fact away). So it can discharge the capacitor more fully down to the rail. Nowadays we might use a mosfet, but at a 1.5V power supply even today it would take a low threshold trench mosfet.
Walt Jung has a web site, where there are links to quite a few of his articles. One that caught my attention is a detailed look at the frequency response of different current source circuits and ICs (including the LM334 and LM317) in the context of distortion in audio circuits.
One thing that catches my attention in that pressure (potentiometer) to frequency converter circuit you linked in post #32 is the large number of transistors it calls out, and the fact that they are discrete garden variety transistors, not an array. The circuit though suggests matched transistors that you would find in an array, as though Bob was in the process of prototyping an integrated circuit around the LM10 core.
Walt Jung hasn't aged a bit - he looks exactly the same as 30 years ago :-)
As for the transistors in Bob's circuit I guess that at least 8 of the NPN's might be of a matched array variety (I circled them in red; and my guess's they're in DIP-14 array flavour if the tiny numbers correspond to equal pins, although 'pin' number 1 is repeated few times within and does NOT correspond dip-14 logic). Certainly a preliminary design for the IC of some kind....
I have the same circuit described at post 1 except one thing. A thermocouple (0...10mA) is connected between pin 2 and right side of R1 or top of R2 (junction of R1 and R2). How to insert the voltage "Usens" to the Iout Formula? I will get a current relative to the voltage from the Sensor.
But I cant get the LTSpice Simulation running The currents from the voltage source are always wrong. Doesnt matter if I use the "sensor voltage to pin 2" or the normal current source circuit.
Comments
0 to 15PSI pressure measurement using V-F circuit powered from 1.5V and with total current drain of about 1mA.
That's how Bob Pease did it in 1980's
The internals of the LM10, and analog ics in general comes from an appreciation of what can be done with transistors that reside on the same substrate. It is a different circuit concept, quite different from the biasing schemes that are necessary with discrete design. Widlar understood bipolar transistors backwards and upside down and took it to the limit in the low voltage design of the LM10. It was one thing to make a 1.2 V bandgap reference, but it took an extra measure of insight to turn that upside down and make a 0.2 V reference that could work and be accurate on a 1.1 V power supply, so close to the bandgap voltage of silicon.
Another writer back in the day was Walt Jung. I totally dog-eared my copy of the IC Array Cookbook. Its was a great introduction to the unique type of analog circuit design possible when you have matched transistors. Walt was engineer and technical writer at Analog Devices, and the first editor of the Linear Tech magazine. His Op-Amp Cookbook, and Audio Circuits Cookbook and others in that series were a great training ground, now all out of print I think.
Here's Jim Williams designs around LM10 in LT Appnote from 1985 (he uses LM10 there as one of the only 2 IC's available to work those wonders at 1.5V at that time). Notice how nonchalantly and almost by-the-way'ish he brings to us "transistor operating in inverted mode'. Say what? Only IEEE papers discussed it at all and there he was using it here and there... I was taught that the transistor in inverted mode goes into an avalanche mode, i.e. dangerous zone and is ready to go pufffffff...
He show me how very little did I know of low battery circuits. Add to that the LT1615 micropower DC-DC http://www.linear.com/product/LT1615 (probably of his design as well) and I might 'never' throw away any AA or AAA :-)
Walt Jung has a web site, where there are links to quite a few of his articles. One that caught my attention is a detailed look at the frequency response of different current source circuits and ICs (including the LM334 and LM317) in the context of distortion in audio circuits.
One thing that catches my attention in that pressure (potentiometer) to frequency converter circuit you linked in post #32 is the large number of transistors it calls out, and the fact that they are discrete garden variety transistors, not an array. The circuit though suggests matched transistors that you would find in an array, as though Bob was in the process of prototyping an integrated circuit around the LM10 core.
As for the transistors in Bob's circuit I guess that at least 8 of the NPN's might be of a matched array variety (I circled them in red; and my guess's they're in DIP-14 array flavour if the tiny numbers correspond to equal pins, although 'pin' number 1 is repeated few times within and does NOT correspond dip-14 logic). Certainly a preliminary design for the IC of some kind....
Plus an intriguing collection of all sort of EE tools here http://www.ganssle.com/tools.htm#Difftools
One can only admire its simplicity and elegance.
I have the same circuit described at post 1 except one thing. A thermocouple (0...10mA) is connected between pin 2 and right side of R1 or top of R2 (junction of R1 and R2). How to insert the voltage "Usens" to the Iout Formula? I will get a current relative to the voltage from the Sensor.