Strategies for temperature-compensating differential pairs
in [Design]
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From: miso on 11 May 2010 15:06 On May 11, 1:42 am, Bitrex <bit...(a)de.lete.earthlink.net> wrote: > m...(a)sushi.com wrote: > > On May 9, 9:44 pm, Bitrex <bit...(a)de.lete.earthlink.net> wrote: > >> Michael Robinson wrote: > >>> "Bitrex" <bit...(a)de.lete.earthlink.net> wrote in message > >>>news:5Yednf5fg-xt1nvWnZ2dnUVZ_rydnZ2d(a)earthlink.com... > >>>> m...(a)sushi.com wrote: > >>>>> On May 8, 8:01 pm, Bitrex <bit...(a)de.lete.earthlink.net> wrote: > >>>>>> John Larkin wrote: > >>>>>>> On Sat, 08 May 2010 20:19:15 -0400, Bitrex > >>>>>>> <bit...(a)de.lete.earthlink.net> wrote: > >>>>>>>> If you put a reference current into the collector of one half of a > >>>>>>>> differential pair, > >>>>>>> You've lost me already. What do you mean by putting a current into the > >>>>>>> collector of a diff pair? Normally one stuffs a current into the > >>>>>>> paralleled emitters. > >>>>>>> Can you post a schematic? > >>>>>>> John > >>>>>> Sorry for not being more clear - in the meantime I was able to find a > >>>>>> website that has an example of the circuit configuration I am talking > >>>>>> about here, figure 3: > >>>>>>http://www.uni-bonn.de/~uzs159/ > >>>>>> It appears from the text the most common way to compensate the 1/T > >>>>>> temperature dependence of the circuit is to use a resistor with a > >>>>>> positive temperature coefficient in the circuit that provides the > >>>>>> control voltage. To make it work well I guess you would want to bind > >>>>>> the differential pair to the tempco resistor with some kind of thermally > >>>>>> conductive adhesive. > >>>>>>> and then take an output current from the collector of > >>>>>>>> the other transistor of a differential pair, the output current as a > >>>>>>>> fraction of the reference current will be compensated against > >>>>>>>> variations > >>>>>>>> of Is. However, because of the dependence of VT on temperature Vbe > >>>>>>>> will > >>>>>>>> now have a positive tempco, and the output current as a fraction of > >>>>>>>> the reference current will decrease with increasing temperature of the > >>>>>>>> pair. I'm wondering what strategies the analog designers here have > >>>>>>>> used > >>>>>>>> to compensate for this second-order temperature dependence? TIA! > >>>>> Looks like frames did you a disservice. It this the page in question? > >>>>>http://www.uni-bonn.de/~uzs159/expo_tutorial/index.html > >>>>> If not, then right click on the link in question and open it in > >>>>> another window to get the correct URL. > >>>> Thanks, that's the correct page. > >>> That guy is such a bad writer. He never gives you the most basic > >>> information: what's the circuit supposed to do, what kind of input signal > >>> goes in, just the most basic stuff that should be the first thing he tells > >>> you. Instead he starts out from nowhere and goes into excructiating detail > >>> about a whole bunch of stuff that has no context. It looks like he's > >>> describing an attempt to build a transconductance amplifier with an > >>> exponential transfer function. And there's a sentence buried deep in the > >>> text, something about in input of one volt per octave, and he wants the > >>> output current to double for a change of one volt in the input signal.. I > >>> haven't figured out whether the circuit he shows is fit for that purpose. > >>> How many octaves (volts) is the input going to vary? How big of a signal > >>> can you put into the circuit he drew? You could spend forever getting lost > >>> in the details. Better to ask first: what's the right approach? > >> It does make more sense when you get to the page above through the > >> main page:http://www.uni-bonn.de/~uzs159/index.html, the material then > >> has some context! > > > I thinks frames messed you up again. I have no idea where you are > > trying to send us. However, I don't think that website is particularly > > useful. Not only is the electronics questionable, but the page refers > > to figures that are not even labeled. > > > SSM and Curtis Electro Music used to make chips for analog > > synthesizers. ADI absorbed SSM. Doug Curtis died a few years ago, and > > he had already folded that company into his design service company. > > THAT makes many of the same analog circuits. I would try to find > > designs from those companies rather than mess with that questionable > > website. > > I've actually built a few circuits around the SSM2044 VCF - I bought > several off Ebay years ago before I understood how large the industry of > IC fakes is. The ones I've used appear to function as intended within > the bounds of what tests I'm able to perform, so who knows, maybe > they're _good_ fakes? :) > > > > > Don't get me wrong. I would like to encourage you to do the analog > > design since nowadays people think engineering is programming a damn > > pic. Just don't put too much faith into one website. This stuff really > > isn't rocket science, but analog can be difficult to understand if it > > is not explained well. > > Thanks for the encouragement - I do some microcontroller programming too > but it's the analog aspect of circuit design that really gets my mind going. Derek Bowers was the guy behind SSM. You can probably find papers from him. Doug Curtis wasn't quite as interested in publishing. Doug has a nice set up. I recall being greeted by a coyote the first time I went to his lair. At the time he had the company run out of his guest house in Los Gatos.
From: Robert Baer on 11 May 2010 23:11 miso(a)sushi.com wrote: > On May 11, 1:42 am, Bitrex <bit...(a)de.lete.earthlink.net> wrote: >> m...(a)sushi.com wrote: >>> On May 9, 9:44 pm, Bitrex <bit...(a)de.lete.earthlink.net> wrote: >>>> Michael Robinson wrote: >>>>> "Bitrex" <bit...(a)de.lete.earthlink.net> wrote in message >>>>> news:5Yednf5fg-xt1nvWnZ2dnUVZ_rydnZ2d(a)earthlink.com... >>>>>> m...(a)sushi.com wrote: >>>>>>> On May 8, 8:01 pm, Bitrex <bit...(a)de.lete.earthlink.net> wrote: >>>>>>>> John Larkin wrote: >>>>>>>>> On Sat, 08 May 2010 20:19:15 -0400, Bitrex >>>>>>>>> <bit...(a)de.lete.earthlink.net> wrote: >>>>>>>>>> If you put a reference current into the collector of one half of a >>>>>>>>>> differential pair, >>>>>>>>> You've lost me already. What do you mean by putting a current into the >>>>>>>>> collector of a diff pair? Normally one stuffs a current into the >>>>>>>>> paralleled emitters. >>>>>>>>> Can you post a schematic? >>>>>>>>> John >>>>>>>> Sorry for not being more clear - in the meantime I was able to find a >>>>>>>> website that has an example of the circuit configuration I am talking >>>>>>>> about here, figure 3: >>>>>>>> http://www.uni-bonn.de/~uzs159/ >>>>>>>> It appears from the text the most common way to compensate the 1/T >>>>>>>> temperature dependence of the circuit is to use a resistor with a >>>>>>>> positive temperature coefficient in the circuit that provides the >>>>>>>> control voltage. To make it work well I guess you would want to bind >>>>>>>> the differential pair to the tempco resistor with some kind of thermally >>>>>>>> conductive adhesive. >>>>>>>>> and then take an output current from the collector of >>>>>>>>>> the other transistor of a differential pair, the output current as a >>>>>>>>>> fraction of the reference current will be compensated against >>>>>>>>>> variations >>>>>>>>>> of Is. However, because of the dependence of VT on temperature Vbe >>>>>>>>>> will >>>>>>>>>> now have a positive tempco, and the output current as a fraction of >>>>>>>>>> the reference current will decrease with increasing temperature of the >>>>>>>>>> pair. I'm wondering what strategies the analog designers here have >>>>>>>>>> used >>>>>>>>>> to compensate for this second-order temperature dependence? TIA! >>>>>>> Looks like frames did you a disservice. It this the page in question? >>>>>>> http://www.uni-bonn.de/~uzs159/expo_tutorial/index.html >>>>>>> If not, then right click on the link in question and open it in >>>>>>> another window to get the correct URL. >>>>>> Thanks, that's the correct page. >>>>> That guy is such a bad writer. He never gives you the most basic >>>>> information: what's the circuit supposed to do, what kind of input signal >>>>> goes in, just the most basic stuff that should be the first thing he tells >>>>> you. Instead he starts out from nowhere and goes into excructiating detail >>>>> about a whole bunch of stuff that has no context. It looks like he's >>>>> describing an attempt to build a transconductance amplifier with an >>>>> exponential transfer function. And there's a sentence buried deep in the >>>>> text, something about in input of one volt per octave, and he wants the >>>>> output current to double for a change of one volt in the input signal. I >>>>> haven't figured out whether the circuit he shows is fit for that purpose. >>>>> How many octaves (volts) is the input going to vary? How big of a signal >>>>> can you put into the circuit he drew? You could spend forever getting lost >>>>> in the details. Better to ask first: what's the right approach? >>>> It does make more sense when you get to the page above through the >>>> main page:http://www.uni-bonn.de/~uzs159/index.html, the material then >>>> has some context! >>> I thinks frames messed you up again. I have no idea where you are >>> trying to send us. However, I don't think that website is particularly >>> useful. Not only is the electronics questionable, but the page refers >>> to figures that are not even labeled. >>> SSM and Curtis Electro Music used to make chips for analog >>> synthesizers. ADI absorbed SSM. Doug Curtis died a few years ago, and >>> he had already folded that company into his design service company. >>> THAT makes many of the same analog circuits. I would try to find >>> designs from those companies rather than mess with that questionable >>> website. >> I've actually built a few circuits around the SSM2044 VCF - I bought >> several off Ebay years ago before I understood how large the industry of >> IC fakes is. The ones I've used appear to function as intended within >> the bounds of what tests I'm able to perform, so who knows, maybe >> they're _good_ fakes? :) >> >> >> >>> Don't get me wrong. I would like to encourage you to do the analog >>> design since nowadays people think engineering is programming a damn >>> pic. Just don't put too much faith into one website. This stuff really >>> isn't rocket science, but analog can be difficult to understand if it >>> is not explained well. >> Thanks for the encouragement - I do some microcontroller programming too >> but it's the analog aspect of circuit design that really gets my mind going. > > Derek Bowers was the guy behind SSM. You can probably find papers from > him. Doug Curtis wasn't quite as interested in publishing. Doug has a > nice set up. I recall being greeted by a coyote the first time I went > to his lair. At the time he had the company run out of his guest house > in Los Gatos. What about John Burgoon(sp?) of Solid State Music 2102A (Kifer?) in Santa Clara CA? I understand that he developed those circuits and with some horsetrading got Exar to make chips for him...resulting in some rather nice analog chips useful for sound and music generation.
From: miso on 12 May 2010 03:25
On May 11, 8:11 pm, Robert Baer <robertb...(a)localnet.com> wrote: > m...(a)sushi.com wrote: > > On May 11, 1:42 am, Bitrex <bit...(a)de.lete.earthlink.net> wrote: > >> m...(a)sushi.com wrote: > >>> On May 9, 9:44 pm, Bitrex <bit...(a)de.lete.earthlink.net> wrote: > >>>> Michael Robinson wrote: > >>>>> "Bitrex" <bit...(a)de.lete.earthlink.net> wrote in message > >>>>>news:5Yednf5fg-xt1nvWnZ2dnUVZ_rydnZ2d(a)earthlink.com... > >>>>>> m...(a)sushi.com wrote: > >>>>>>> On May 8, 8:01 pm, Bitrex <bit...(a)de.lete.earthlink.net> wrote: > >>>>>>>> John Larkin wrote: > >>>>>>>>> On Sat, 08 May 2010 20:19:15 -0400, Bitrex > >>>>>>>>> <bit...(a)de.lete.earthlink.net> wrote: > >>>>>>>>>> If you put a reference current into the collector of one half of a > >>>>>>>>>> differential pair, > >>>>>>>>> You've lost me already. What do you mean by putting a current into the > >>>>>>>>> collector of a diff pair? Normally one stuffs a current into the > >>>>>>>>> paralleled emitters. > >>>>>>>>> Can you post a schematic? > >>>>>>>>> John > >>>>>>>> Sorry for not being more clear - in the meantime I was able to find a > >>>>>>>> website that has an example of the circuit configuration I am talking > >>>>>>>> about here, figure 3: > >>>>>>>>http://www.uni-bonn.de/~uzs159/ > >>>>>>>> It appears from the text the most common way to compensate the 1/T > >>>>>>>> temperature dependence of the circuit is to use a resistor with a > >>>>>>>> positive temperature coefficient in the circuit that provides the > >>>>>>>> control voltage. To make it work well I guess you would want to bind > >>>>>>>> the differential pair to the tempco resistor with some kind of thermally > >>>>>>>> conductive adhesive. > >>>>>>>>> and then take an output current from the collector of > >>>>>>>>>> the other transistor of a differential pair, the output current as a > >>>>>>>>>> fraction of the reference current will be compensated against > >>>>>>>>>> variations > >>>>>>>>>> of Is. However, because of the dependence of VT on temperature Vbe > >>>>>>>>>> will > >>>>>>>>>> now have a positive tempco, and the output current as a fraction of > >>>>>>>>>> the reference current will decrease with increasing temperature of the > >>>>>>>>>> pair. I'm wondering what strategies the analog designers here have > >>>>>>>>>> used > >>>>>>>>>> to compensate for this second-order temperature dependence? TIA! > >>>>>>> Looks like frames did you a disservice. It this the page in question? > >>>>>>>http://www.uni-bonn.de/~uzs159/expo_tutorial/index.html > >>>>>>> If not, then right click on the link in question and open it in > >>>>>>> another window to get the correct URL. > >>>>>> Thanks, that's the correct page. > >>>>> That guy is such a bad writer. He never gives you the most basic > >>>>> information: what's the circuit supposed to do, what kind of input signal > >>>>> goes in, just the most basic stuff that should be the first thing he tells > >>>>> you. Instead he starts out from nowhere and goes into excructiating detail > >>>>> about a whole bunch of stuff that has no context. It looks like he's > >>>>> describing an attempt to build a transconductance amplifier with an > >>>>> exponential transfer function. And there's a sentence buried deep in the > >>>>> text, something about in input of one volt per octave, and he wants the > >>>>> output current to double for a change of one volt in the input signal. I > >>>>> haven't figured out whether the circuit he shows is fit for that purpose. > >>>>> How many octaves (volts) is the input going to vary? How big of a signal > >>>>> can you put into the circuit he drew? You could spend forever getting lost > >>>>> in the details. Better to ask first: what's the right approach? > >>>> It does make more sense when you get to the page above through the > >>>> main page:http://www.uni-bonn.de/~uzs159/index.html, the material then > >>>> has some context! > >>> I thinks frames messed you up again. I have no idea where you are > >>> trying to send us. However, I don't think that website is particularly > >>> useful. Not only is the electronics questionable, but the page refers > >>> to figures that are not even labeled. > >>> SSM and Curtis Electro Music used to make chips for analog > >>> synthesizers. ADI absorbed SSM. Doug Curtis died a few years ago, and > >>> he had already folded that company into his design service company. > >>> THAT makes many of the same analog circuits. I would try to find > >>> designs from those companies rather than mess with that questionable > >>> website. > >> I've actually built a few circuits around the SSM2044 VCF - I bought > >> several off Ebay years ago before I understood how large the industry of > >> IC fakes is. The ones I've used appear to function as intended within > >> the bounds of what tests I'm able to perform, so who knows, maybe > >> they're _good_ fakes? :) > > >>> Don't get me wrong. I would like to encourage you to do the analog > >>> design since nowadays people think engineering is programming a damn > >>> pic. Just don't put too much faith into one website. This stuff really > >>> isn't rocket science, but analog can be difficult to understand if it > >>> is not explained well. > >> Thanks for the encouragement - I do some microcontroller programming too > >> but it's the analog aspect of circuit design that really gets my mind going. > > > Derek Bowers was the guy behind SSM. You can probably find papers from > > him. Doug Curtis wasn't quite as interested in publishing. Doug has a > > nice set up. I recall being greeted by a coyote the first time I went > > to his lair. At the time he had the company run out of his guest house > > in Los Gatos. > > What about John Burgoon(sp?) of Solid State Music 2102A (Kifer?) in > Santa Clara CA? > I understand that he developed those circuits and with some > horsetrading got Exar to make chips for him...resulting in some rather > nice analog chips useful for sound and music generation. When I was at Exar, my understanding is Bowers did the designs. SSM was buying analog gate arrays from Exar. I did not have first hand knowledge of this since I worked in a different group. I thought SSM was folded into ADI. You find SSM datasheets on the ADI website: http://www.analog.com/en/audiovideo-products/audio-signal-processors/ssm2019/products/product.html If you look at Exar today, they don't have the bipolar product line to make the SSM style chips (unless they don't put it on the website). Back in the day, Exar was getting their bipolar from Rohm in some bizarre deal that never made sense to me (well at least from Rohm's end). The two companies have been disconnected for years. |