Lets talk about VCOs

Thread Starter

Wendy

Joined Mar 24, 2008
21,914
Recently I released a design for what I hope is a Precision Diode Wideband AC-DC converter. It got me to thinking If I coupled this to a linear sweep generator and a wide rang VCO 100Hz-200 KHz With an oscope I might have the basis for a network analyzer. The key is the VCO. My first thought is to make Schmitt trigger with variable set points similar to how a 555 does it and make a hysteric Oscillator ( I'll draw and post the concept later but it occurs to me that someone has a better idea, So here I am hat in hand asking for ideas, and no, I have not Googled it yet.
 
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OBW0549

Joined Mar 2, 2015
3,097
My first thought is to make Schmitt trigger with variable set points similar to how a 555 does it and make a hysteric Oscillator ( I'll draw and post the concept later but it occurs to me that someone has a better idea, So here I am hat in hand asking for ideas, and no, I have not Googled it yet.
A while back I built a voltage-controlled oscillator using a That Corporation 2180 VCA as a voltage-controlled current source, a FET op amp with low input bias current, and a CMOS 555 as the hysteresis element (NOTE: the control voltage is applied to the EC+ pin of the THAT2180, pin 2):
VCVGA Osc.png
It worked very well over a 1 Hz - 20 kHz range, with a good, clean triangle wave on the op amp output and a square wave on pin 3 of the LMC555; I imagine that with a faster op amp it would go higher in frequency, but I didn't check.
 

DECELL

Joined Apr 23, 2018
96
Anyhow- back to your idea Wendy, if indeed that is your real name!
Can we see your wide band detector?
 
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Thread Starter

Wendy

Joined Mar 24, 2008
21,914
Sure my name is Wendy Jean Marsden wasn't always, but it has been legally changed and everything. I'll modify my 1st post in this thread to include the link.

Wendy's Index
 
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