[sdiy] Linear current source - temperature compensation?

Ben Bradley ben.pi.bradley at gmail.com
Sat Nov 12 23:39:05 CET 2016

Woops, my earlier response only went to Justin:
>I recall the original PAIA (linear VCO/VCF) circuits, you can make a
linear-controlled current source easily that doesn't need temperature
compensation, with just one opamp and one transistor.

A linear current source doesn't rely on Vbe or the exponential
response of collector current to Vbe (both things temperature
sensitive). The current through the collector is determined by the
emitter voltage and the current through its resistor to ground, which
is controlled within the opamp's feedback loop. Here's an old PAIA
schematic showing what I was thinking of, The current goes into the
capacitor and UJT used as an oscillator, thus this is a linear VCO:


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