Just a few questions regarding the "Thompson current mirror" here:
First, is it possible to obtain more than one output from this mirror? It does not appear obvious how to do it, as opposed to the straightforward way to get multiple outputs from, say, the "bare" current mirror.
Second, is it possible to adapt this mirror for use as the load for a differential pair? The requirement for two input current sources seems to make this difficult.
Thanks!
The "Thompson current mirror" resulted from a coffee bet with Tom Frederiksen (back around 1964) where Tom opined I couldn't make a useful PNP mirror with the really crappy lateral PNP's of that era.
I won the bet ;-)
I never really considered multiple outputs but, clearly, in an integrated circuit environment with good matching, just use multiple instances of Q15 (QP). To enhance matching perhaps pad a resistor in each PNP emitter. (And allow for the extra "diversion" currents... it is, after all, a Kirchhoff circuit... what goes in must come out ;-)
Page 7 of that PDF shows how it's done in the MC1494.
If what you mean is a differential-to-single-ended turn-around please advise and I'll sketch something up. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Thanks for the reply. I don't fully understand what's going on in that circuit, unfortunately. I guess what I had in mind was something like the first stage in a conventional op amp?
Generally the first stage of an OpAmp IS a differential-to-single-ended turn-around.
Is that your need?
Or are you wanting to continue on differentially?
In the latter case that's usually implemented with a common-mode loop.
Let me know which and I'll sketch it out for you.
And it makes a difference... are we dealing with lateral PNP's or do you want it in CMOS?
(I've even done mixed devices, using CMOS to cascode PNP's ;-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Yes, that'd be nice :)
Bipolar would be good. This is not a chip design, I'm just mucking about with discretes for fun. Thanks!
OK. Tomorrow. It's now wine sipping time, while we watch O'Reilly ;-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Here's the rest of the schematic... cunningly hidden as MC1594 on Jim's site :) Thanks google!
Clifford Heath.
I have a few: Just for grins, swap Q11,Q12 on page 4 and compare results with the others. How about temperature curves for all of them (include my "bastard" one)?
I'm only up to "H" in my indexing efforts, and it's boring, tiring work ;-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
It'll saturate. Did you try it in LTspice where default transistors are perfect?
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Not yet. Fer starters, the interchange makes that part exactly like the "BARE" circuit; Q13 the load. Which seems it cannot work due to no bias..so another transistor would be needed. Oh well, was a quickie idea anyway.
Hey, it's after tomorrow! How's it coming? :)
It's written, not yet PDF'd. In the morrow, ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
From: Jim Thompson Newsgroups: alt.binaries.schematics.electronic Subject: Q for Jim Thompson (Bitrex, S.E.D) - MirrorWriteup.pdf Date: Sun, 25 Aug 2013 13:56:20 -0700 Message-ID: ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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