Exponential converter: Difference between revisions
No edit summary |
m (Text replacement - "home.comcast.net/~ijfritz" to "ijfritz.byethost4.com") |
||
Line 19: | Line 19: | ||
* [http://yusynth.net/Modular/EN/VCO/ yusynth VCO] |
* [http://yusynth.net/Modular/EN/VCO/ yusynth VCO] |
||
* [https://web.archive.org/web/20150109082220/http://www.amsynths.co.uk/Old_Stuff/Oscillators/oscillators.html Oscillators – At The Source] |
* [https://web.archive.org/web/20150109082220/http://www.amsynths.co.uk/Old_Stuff/Oscillators/oscillators.html Oscillators – At The Source] |
||
* [http:// |
* [http://ijfritz.byethost4.com/sy_cir7.htm Tempco Equations] |
||
* A couple of pages about tempcos linked from [http:// |
* A couple of pages about tempcos linked from [http://ijfritz.byethost4.com/sy_over.htm Synthesizer Projects and Schematics] by Ian Fritz |
||
* [http://www.openmusiclabs.com/files/expotemp.pdf Thermal Compensation of Analog Exponential Converters], openmusiclabs, March 2015 |
* [http://www.openmusiclabs.com/files/expotemp.pdf Thermal Compensation of Analog Exponential Converters], openmusiclabs, March 2015 |
||
* [http://www.milton.arachsys.com/nj71/index.php?menu=2&submenu=2&subsubmenu=9 On Oscillator Linearity and Musicality] by [[Neil Johnson]] |
* [http://www.milton.arachsys.com/nj71/index.php?menu=2&submenu=2&subsubmenu=9 On Oscillator Linearity and Musicality] by [[Neil Johnson]] |
Revision as of 08:29, 29 June 2019
An exponential pair refers to a pair of matched PNP transistors, forming an exponential voltage-to-current converter.
Early synthesizer VCOs (voltage controlled oscillators) were difficult to keep in tune. For a stable analogue audio VCO, the design solution in use since the 1970s has been to use a pair of matched PNP transistors, to form an exponential voltage-to-current converter. The input base-emitter voltage is exponentially related to the collector current. By having the second transistor configured, so that its current is in the opposite direction to the first, most of the temperature dependence is cancelled out. Any remaining temperature dependence is dealt with by using a positive temperature coefficient thermistor (tempco) in thermal contact with the matched transistor pair, in the feedback path of an op-amp voltage summer at their input.[1]
See also
References
Further reading
- Electronic Music Circuits by Barry Klein, The Exponential Converter, pp. 83-87
External links
- Electronotes Supplement S-019 Exponential/Log
- A tutorial on exponential convertors and temperature compensation by René Schmitz
- Thomas Henry VCO-1
- Temperature Compensated VCO
- yusynth VCO
- Oscillators – At The Source
- Tempco Equations
- A couple of pages about tempcos linked from Synthesizer Projects and Schematics by Ian Fritz
- Thermal Compensation of Analog Exponential Converters, openmusiclabs, March 2015
- On Oscillator Linearity and Musicality by Neil Johnson
- temp. comp. with transistors rather than thermistor?, Muff Wiggler forum, Oct 2014
- Exponential converters and how they work