triangular wave generator

[aborigini]

I am designing this triangular wave generator for 250kHz using schmitt triggger.

The triangular wave is not linear and there are jitters at the rising slope. ANyone knows the root of the problem?

Is that to do with the changing of output impedance?

Any other suggestion to generate triangular wave oscillator other than schmitt trigger?

thanx in advance

 

[VVV]

What charges up the capacitor? How is that implemented?

Normally, a current source or an opamp acting as a current source will do the job, so if the current is not constant, then the ramp will not be linear. That is the first thing I would check.

 

[aborigini]

Thank you for the reply.

I am using the circuit shown below.

The op-amp is a single stage folded cascode.

From the waveform it seems there is a high frequecny component in the loop.

Is the problem with the op-amp?

Thank you

 

[VVV]

I don't really think it's the opamp.
Most likely the power supply decoupling. Try adding some good ceramic caps to the power of the opamp, really cose to the package.

Also, check the square wave output of the comparator. That is what you intergrate, so if there is a problem there, you will see it on the triangle, too.
Again, I suspect the power supply decoupling. If the comparator is a separate package, add decoupling to it, too.

 

[aborigini]

Thank you for the input, but this is actually done in a simulation.
The op-amp is self-designed, it is a folded-cascode, single stage amplifier.

That is why I thought it is the op-amp-problem.

The pulses is not clean waveform, there are some jitters at both low and high voltage.

Thank you.

 

[10kangstroms]

Have you compensated the op amp for unity gain stability? It may be oscillating.

 

[roykyn]

TO GENERATE A TRIANGLE WAVE WE HAVE TO USE R & C THERE WILL BE JITTERS DUE TO THAT

Added after 5 minutes:

THIS CKT MIGHT HELP U....

 

[aborigini]

Have you compensated the op amp for unity gain stability? It may be oscillating.

Yup, I have made the compensation and making sure sufficient current in the integrator.

Btw, I have solved the issue. thx!

 

[10kangstroms]

Have you compensated the op amp for unity gain stability? It may be oscillating.

Yup, I have made the compensation and making sure sufficient current in the integrator.

Btw, I have solved the issue. thx!

Don't leave us hanging! What was the solution to your problem?

 

[aborigini]

Errr.. actually I am not sure whether this is a good idea. But from the waveform obtained, it seems there was high frequency component in the waveform. So I added small caps just to remove those unwanted 'distortion'.

What do you think?

 

[10kangstroms]

Errr.. actually I am not sure whether this is a good idea. But from the waveform obtained, it seems there was high frequency component in the waveform. So I added small caps just to remove those unwanted 'distortion'.

What do you think?

Did you put decoupling caps on the power supplies? Op amps may oscillate if you don't.
I think you need to post your schematic.

 

[Verba]

May be you should check the input impedance of the opamp.
If it's not linear with the input voltage swing, it may cause nonlinearity of the trtiangle wave. Zin ~ Rin||(1/SCin), so it may change both, R and C of the integrator. I would try to increase C and decrease R, may be it will help.

 

[funster]

you can use counter and ROM lookup table (DDS) to generate

triangle wave.

best regards

I am designing this triangular wave generator for 250kHz using schmitt triggger.

The triangular wave is not linear and there are jitters at the rising slope. ANyone knows the root of the problem?

Is that to do with the changing of output impedance?

Any other suggestion to generate triangular wave oscillator other than schmitt trigger?

thanx in advance

 

[Vamsi Mocherla]

The capacitors may be added at the output of the opamp as load because that is where the stability needs to be looked upon. Remember that it is a single stage opamp and hence shall be load compensated. Also put a capacitor in parallel to R4 resistor.

 

[ng wei]

may i know the solution of the circuit for triangle wave generatorusing dc power supply?