[sdiy] Electro Notes, #87, pg 18 March 1978

[Oren Leavitt]

Hi David,

You will also have to adjust the 100K resistor that is between the 
output of the 301 summing amp and the base of the 2N3904.

FWIW, I would try first building the circuit using a standard 1.8K 
resistor just to get it working, and then see if the tempco is really 
needed for your application.

Enjoy!
- Oren

David Ingebretsen wrote:
> In my quest for a delay using the MN3005, I found this gem in Electro Notes,
> #87, pg 18, March 1978.
> 
> I have a question on the schematic, please. There is an exponential VCO
> using a 2N3904, and 2N3906. The tempco is from the base of the 2N3904 to
> ground. There is a 470K from the base to the positive supply. Now, I have
> some 2K and 1K tempcos.
> 
> So, this looks like a simple voltage divider so can I use a 523K and a 2K
> tempco, or a 261K and a 1K tempco instead? Am I missing something else?
> There is a 0.01 mFD cap from the base to ground as well. Does this screw me
> up?
> 
> (Is Jan Hall, the author of the schematic on this list?)
> 
> Thanks
> David 
> 
> David M. Ingebretsen M.S., M.E.
> Collision Forensics & Engineering, Inc.
> 2469 East Fort Union Blvd. STE 114
> Salt Lake City, UT 84121
> www.CFandE.com
> 
> 801 733-5458 Office
> 801 842-5451 Cell
> 
> dingebre at CFandE.com
> dingebre at 3dphysics.net
> 
> 
> 
> 
> 
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