[sdiy] Diode to restart CCO core.

[René Schmitz]

Hi Karl and all,

karl dalen schrieb:
> Why would it be a bad idea to use a diode coupled NPN or a NPN for 
> that matter to charge integrator cap? (CCO core). Rene uses 2 regular
> serialized diodes shunted by a 1M resistor in his VCO4, i tested various
> diodes and many seams to leak to much but a diode coupled NPN seams to
> work well.

Interesting, I've never tried that. I only experimented with diode 
connected JFETs (D,S tied) as low leakage diodes.

> Assume typical Moog VCO (but reversed comparator function)
> or Renes VCO4, the diode/NPN switch should work well yes?

I think so, yes. Must try that in a VCO4069 some time, there I also used 
diodes as discharge element.

> With 1n cap at 22c deg i get a (min leakage) cycle of 45sec
> with the diode coupled NPN.(yes its temp sensitive but is
> it worser then a regular J-FET in atypical SAW cco app?

What was the amplitude? Then one can directly calulate the current.

Cheers,
  René

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uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159