Triangle Wave generation

[saad]

Hello,
h**p://www.play-hookey.com/analog/triangle_waveform_generator.html shows a circuit for ramp (triangle wave) generation. I have tried to simulate this circuit in spice but it does not work. All I see is constant DC output

Am I making some mistake or I need to give extra stimulus?

Regards,
Saad

 

[A.Anand Srinivasan]

i think you have made a mistake in the op amp for the square wave part.....
try simulating this....

 

[saad]

i think you have made a mistake in the op amp for the square wave part.....
try simulating this....

this connection is to -ive power supply of the comparator.. i dont think this is mistake..

 

[IanP]

That circuit from **broken link removed** works under condition that opamps are fed from +V, 0V and -V ..

If you want to operate from single power supply, you have to create virtual ground of 1/2* V1 and connect (+) input of IC1 and (-) input of IC2 to that potential ..
Otherwise, this circuit won't work at all ..
http://tangentsoft.net/elec/vgrounds.html

Regards,
IanP

 

[A.Anand Srinivasan]

what i meant is that the V- of the second opamp was connected to ground in that circuit and you have connected it to the negative supply...

 

[RobertKeeley]

This might help sir. Using the virtual ground information the other people have offered, you need a connection similar to this:

 

[rauol]

Use NE556

 

[Sadegh.j]

Could you give me the saturation voltages of your first op amp, the one that produces the triangular wave. Something else, is the power supply correctly connected to the second op map, the one to the right.

 

[saad]

I have connected -ive of comparator to 0.9V supply (i.e. Vref of Comparator). Circuit still does not work

 

[A.Anand Srinivasan]

what about the V+ input of the triangle wave generating opamp... have u connected it to 0.9V or ground.....

 

[saad]

what about the V+ input of the triangle wave generating opamp... have u connected it to 0.9V or ground.....

Rest of the circuit is same as in the figure..i did not change anything else!