[sdiy] Linear current source homework problem

[Scott Gravenhorst]

The FatMan at http://www.paia.com (schematic is available there) uses this method, though
to reduce the error caused by current supplied to the summing node through the EB circuit
of the transistor, a Darlington pair is used.  It is also possible to get even better
performance (accuracy) using a MOSFET instead of a BJT or Darlington.  See the FatMan VCO
 for the Darlington method, the VCA and VCF also use a linear current source and they use
the less accurate single BJT method.

Aaron Lanterman <lanterma at ece.gatech.edu> wrote:
>
>In class, I covered the use of an op amp and a BJT to creat a linear 
>voltage-to-single-ended current source (or sink). Hal Chamberlin uses one 
>as an example of a linear controlled VCA.
>
>I want to create a homework problem where the students look at one in a 
>real synth circuit... oddly, I can't seem to find an example of this sort 
>of circuit beyond used (beyond the Chamberlin book). Can anyone think of 
>one? (I looked at Ray's linear VCA circuit, but it doesn't use a BJT in 
>the current source).
>
>- Aaron
>
>-----------------------------------------------------------------------------
>
>Dr. Aaron Lanterman, Asst. Prof.
>and Demetrius T. Paris Junior Prof.    Voice:  404-385-2548
>School of Electrical and Comp. Eng.    Fax:    404-894-8363
>Georgia Institute of Technology        E-mail: lanterma at ece.gatech.edu
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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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