Osc reset time

[Fraser, Colin J]

> -----Original Message-----
> From: Haible Juergen [mailto:Juergen.Haible at nbgm.siemens.de]
> Sent: 17 December 1998 11:29
> To: DIY; Fraser, Colin J
> Subject: AW: Osc reset time
> 
> You still can build a V in / V out expo converter and a linear
> current source. This was tricky when 741 was the standard
> opamp, but nowadays we have LF411's for low offset voltage
> drift ...

Do you know of anywhere I might find a schematic of such an expo convertor ?
Do I just use a normal expo convertor with the output current passing thru a
resistor and extract the voltage across the resistor ?
What constitutes a stable linear current source ? Will a transistor in the
feedback path of an op-amp do ?

> 	>I'll add a proper expo converter with 1v/oct cv input at the
> weekend and see
> 	>how it performs.
> 
> I'm curious if the finite resistance of the switches has an effect
> on the waveform. 

Me too. The on resistance for the 4066 is 80 ohms max. Given that in a
normal osc the cap would be connected to the +v supply, how much extra
resistance does the switch present in addition to the output of the supply
regulator ?
And what sort of impedance does a typical current source have ? 
Come to think of it, what sort of series resistance does a capacitor have ?
(Wish I'd taken a degree in electronics instead of computing !)

I expect I will need to experiment more over the weekend to determine if
this design will be stable enough.

Colin f