Using Op Amps to create rectified triangle wave

[srobertjames]

I'm trying to create a triangle wave that goes roughly from +100mV to close to max +V. I built a square wave using a 555 going from -V to +v, and can convert it to a triangle wave centered on ground using an op amp integrator.

But - I'm having trouble shifting the triangle wave to where I need it. But I'm having trouble shifting it to where I need it (i.e. completely on the positive side of ground). I tried capacitve coupling, but got a weird result. I tried using an op amp averager to +v, but also got weird results.

Does the integrator have a low output impedance? Do I need to buffer it?

Am I doing something else wrong?

What's the preferred way of doing this shift?

 

[vne147]

Maybe you're just using the opamp for fun and you know about this IC already. Or maybe you just read the giant warning at the top of the data sheet but just in case, check this out:

Precision Waveform Generator/Voltage Controlled Oscillator

 

[crutschow]

If you post a schematic of what you are doing, we could give better suggestions as how to improve it. What is the frequency?

Otherwise vne147's suggestion to use the ICL8038 waveform generator instead is good.

 

[srobertjames]

Frequency is 500-1000 Hz.

Alas, the Intersil chip is not to be found - do you know of any similar ones that are available (DIP only, no SMT)?

 

[vne147]

NTE864 is an equivalent IC. I think it's rapidly becoming as hard to aquire as the ICL8038. My local electronics shop might still have a few. I'm going there later today so I can check for you. If they have one I'll be happy to ship it to you if you pay for the cost+shipping. If they don't have it, I think I might have one lying around that I could send to you for the same (cost+shipping).

 

[crutschow]

Try the 2206 instead.

 

[MikeMl]

Look here ... ... ... ... ... ....