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TrevorG3VLF · 9th Nov 2018, 6:43 pm

Passive circuit with gain greater than one.
I assume that the phase shift is zero.

There is an old book by Dean (p197) which I cannot find. This used a pair of pnp transistors in a Darlington pair to get high input resistance and low output resistance.

There were three capacitors in series, two were driven by 47k resistors, the third went to the transistor base.
With C=80microF, 1cycle/minute
With C=100nF, 11Hz
I believe this low frequency system was used to generate vibrato in electronic organs.

9th Nov 2018, 6:43 pm	#22
TrevorG3VLF Rest in Peace Join Date: Apr 2011 Location: Matlock, Derbyshire, UK. Posts: 1,378	Re: Playing with valve oscillators Passive circuit with gain greater than one. I assume that the phase shift is zero. There is an old book by Dean (p197) which I cannot find. This used a pair of pnp transistors in a Darlington pair to get high input resistance and low output resistance. There were three capacitors in series, two were driven by 47k resistors, the third went to the transistor base. With C=80microF, 1cycle/minute With C=100nF, 11Hz I believe this low frequency system was used to generate vibrato in electronic organs.