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debterminer
Joined: Feb 11, 2014
Posts: 41
Location: washington, US
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 Posted: Mon Jun 15, 2015 8:36 pm Post subject:
Self heating ca3046 exponential converter |
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Hello, im looking for any schematics or information relating to a exponential converter design i read about(which was at one point implemented in the moog prodigy) for a self heating ca3046 exponential converter.
What i have read is that the moog prodigy exponential converter used a single ca3046, and used one of the transistors on board the ca3046 to heat the chip instead of a tempco.
Im wondering if anyone has a schematic for this type of exponential converter design using the ca3046, or any information regarding this kind of design? |
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blue hell
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Joined: Apr 03, 2004
Posts: 24373
Location: The Netherlands, Enschede
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debterminer
Joined: Feb 11, 2014
Posts: 41
Location: washington, US
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| Posted: Tue Jun 16, 2015 6:29 pm Post subject:
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| Jan what should I read to understand the article posted "http://electronotes.netfirms.com/s019.pdf" I do not grasp even its first paragraph :X |
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elmegil
Joined: Mar 20, 2012
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debterminer
Joined: Feb 11, 2014
Posts: 41
Location: washington, US
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| Posted: Tue Jun 16, 2015 10:40 pm Post subject:
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| Thank you, i'll check those out. If anyones got any more relevant information i welcome it.[/i] |
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blue hell
Site Admin
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Location: The Netherlands, Enschede
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| Posted: Wed Jun 17, 2015 4:47 am Post subject:
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| debterminer wrote: | | Jan what should I read to understand the article posted "http://electronotes.netfirms.com/s019.pdf" I do not grasp even its first paragraph :X |
Just skip that then and go to fig 6. on page 4 and the paragraph of text around that - where the heater / thermostat circuit is drawn out and explained.
You can then use two other transistors to make a standard expo converter.
Just keep in mind that the substrate of the transistor array should be at the most negative voltage in the circuit .. see the data sheet for that best. It is coupled to one of thee transistors and you could decide to not use that one.
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Jan
also .. could someone please turn down the thermostat a bit.
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debterminer
Joined: Feb 11, 2014
Posts: 41
Location: washington, US
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| Posted: Wed Jun 17, 2015 9:19 pm Post subject:
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| thank you very much |
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Broadwave
Joined: Feb 16, 2007
Posts: 347
Location: Manchester UK
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| Posted: Wed Jun 17, 2015 9:57 pm Post subject:
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Take a look at the Dopefer VCO schematics - I've used the heater section to stabilize several Frequency Central System X VCOs with great results.
http://www.doepfer.de/a110_tec.htm
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debterminer
Joined: Feb 11, 2014
Posts: 41
Location: washington, US
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| Posted: Thu Jun 18, 2015 2:09 pm Post subject:
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| thank you andy |
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forbin
Joined: Jan 29, 2009
Posts: 120
Location: Fremantle, Australia
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| Posted: Fri Jun 26, 2015 6:18 pm Post subject:
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| If you use elements of the doepfer design dont forget the biasing on the extra transistor to the left (transistor on its own with two resistors). Jan also mentioned this earlier but it may not be apparent. Most of the common arrays have protection diodes and you need to make sure that the substrate pin is at the lowest potential of any of the other pins... Made that mistake in redrawing a moog 921b oscillator pcb... Sadness will ensue... |
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debterminer
Joined: Feb 11, 2014
Posts: 41
Location: washington, US
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| Posted: Wed Jul 01, 2015 10:44 am Post subject:
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| So im under the impression it should be at the supplys negative voltage rail?(-15v) |
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wackelpeter
Joined: May 05, 2013
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| Posted: Thu Jul 02, 2015 1:03 am Post subject:
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don't have to be -15V for each application i would say... maybe in your case it's right
have a look at Yves Usson's Moog or EMS filter... in one design it's directly to ground and in the other to -9V via resistor...
i guess that means the most negative potential you will have at this Array should or must be connected to pin 13 the substrate...
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blue hell
Site Admin
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Location: The Netherlands, Enschede
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| Posted: Thu Jul 02, 2015 2:41 am Post subject:
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| wackelpeter wrote: | | i guess that means the most negative potential you will have at this Array should or must be connected to pin 13 the substrate... |
Yes, that is the thing to do. There probably is some maximum voltage involved as well between any pin and thee substrate. The data sheet will, or should at least, mention that. Anyways, that might be a reason to not just connect it to -15V.
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Jan
also .. could someone please turn down the thermostat a bit.
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