[sdiy] Resistor matching in Bergfotron complex VCO

[Paul Perry]

I expect Tim is right on this.
Whenever I have seen a triangle generator that was asymmetric only at low
frequencies, it was due to the charge/discharge currents (tiny at low
frequencies) being themselves asymmetric, due to input leakage current in
the op amp.

paul perry Melbourne Australia

-----Original Message-----
Since the lack of symmetry would tend to indicate some imbalance in the
current into/out of the main timing cap, are you using high input impedance
op amps like the TL072s shown on the Bergfotron schematics? If a
bipolar-input type, could the input bias current be causing grief? A quick
calculation suggests this idea might be a bit iffy, but it was just a
thought...
Tim Stinchcombe 
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