opamp sawtooth voltage generation

[polarized]

opamp sawtooth

Hello everyone,

I am using a double operational amplifier, the first one is a square wave oscilator and the second one is the integrator of the previous stage. The operational amplifiers power supply is symetrical at the moment, +9V and -9V. I am using a miniature switching circuit to generate -9V. I was thinking is it possible to generate a sawtooth voltage form by powering the opamps from a single power supply, for example only +9V. In this way, I would not need the switching circuit. Can the integrator produce a negative slope if the opamp is powered by a single power supply? Thanks.

 

[VVV]

op amp sawtooth

If both opamps are powered from the same unsymmetrical power supply, then yes, you will obtain the same waveforms.

The only difference is that the sawtooth is no longer centered around zero, but around half your power supply. So if you are running at 9V, the sawtooth will be centered around 4.5V. If that is not a problem for you, then everything is fine.

 

[bateAz]

sawtooth generation op amp

Take care of some possible problems.
1. I don't know what type of OA are You using, but ussualy OA have no rail-to-rail output and 'low' and 'high' output voltages of the square wave oscilator would be unsymmetrical according to power supply. For example : Low 0.4V and High 7.5V ( not 8.6V, which matches 0.4V ). This will cause different slopes of the 'falling' and 'rising' ones.
2. "+" input of the second OA have to be connectod to the voltage divider, made by two 1% resistors, f.e. 10kOhm