Exponential converter implementation

Thread Starter

Tacumeon1980

Joined Nov 7, 2020
2
Need help with exponential converter implementation. It will be used for input of synthesizers vco.
VCO simulation works with dedicated current source (attachment1) but when i try to add exponential converter (attachment2) no current goes through Q3. Seems like i missing some basic understandig of bipolar transistor schemes, so i ask for help. That converter should replase input stage of synthesizer, marked in 3rd attachment.
 

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ericgibbs

Joined Jan 29, 2010
13,597
hi 1980,
Welcome to AAC.
The left side image #1 is not connected in the same way as the 'ringed' section in image 3, also there are different components being used.
Are you trying reverse engineer image #3.?
E
 

Thread Starter

Tacumeon1980

Joined Nov 7, 2020
2
hi 1980,
Welcome to AAC.
The left side image #1 is not connected in the same way as the 'ringed' section in image 3, also there are different components being used.
Are you trying reverse engineer image #3.?
E
Yes. First two is my simulations in multisim with idealized components. Third is schematics of Korg monotron duo synthesizer. I've added it to be more clear. My goal is to replace ringed part on that scheme with exponential converter.
 

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