quadrature oscillator??

Hello everyone, I'm having trouble building a quadrature oscillator. The two circuits I have tried building are the quadrature oscillator from this article -

https://www.electro-tech-online.com/custompdfs/2009/01/aug_07.pdf

and this one

Quadrature Oscillator Circuit - www.ECELab.com

I can't get either of them to oscillate - instead the outputs of the op-amps are all at ground. I have tried using 741's and a TL082 and no luck with either. Does anyone have any advice and/or know how I could debug the circuits?

any help would be much appreciated
Philip

In the top one (pdf file) what was your source of 2.5V?
In the bottom one (ECELab) what voltages did you connect to Vee and Vcc?

The minimum supply voltage of a lousy old 741 opamp is 10V or more.
The minimum supply voltage for a TL082 is 7V or more.
They probably don't work when the supply is only 5V.

That is why modern opamps were used in the projects and were selected because they work perfectly when the supply voltage is 5V.

those do tend to be finicky... do you need the since waves? quadrature is easy in the digital realm.

Dan

kchristie -

for the first one, I tried it two different ways. First with the op-amp connected to a + and - supply of everything between 1 and 15 volts +/- . I cannot see why this would make a difference to connecting the negative supply to ground and using 2.5V as what is essentially the ground.... BUT I did that too, using a single rail power supply and getting 2.5V with a potential divider.

audioguru -

i tried both with a wide range of voltages from an old weir power supply, the power supply doesn't seem to be the problem...

ubergeek63 -

The oscillator is for what is essentially a suppressed sideband modulator. I could use a triangle wave but not really a square wave. Sine wave is the most appropriate, if possible! do you have any ideas for a triangle??

digital quad driving integrators

Dan