XR-8038 square wave generator

I am wanting to use a XR-8038 as a signal generator to control an IGBT transistor. I need a positive bias to turn the transistor on and a negative bias to turn the resistor off. I need to do this at 20KHz, 28KHz and 40KHz.

I have the XR-8038 wired to a +/-12V power supply, and get very nice square wave output. The output is 0V to+12V when the ground of the oscilloscope probe is grounded to the common, and -12V to 0V when the probe is grounded to the negative power supply. The circuit is wired according to the Generalized Test Circuit on the datasheet.

**broken link removed**

The question is, how do I get a square wave that is +12V to -12V, or shift the wave to +6V to -6V?

Thank you for your time.

JT

Check that you actually have RL between +15V and the square wave output.

Now that I see your edited post, my response doesn't make any sense. I'd say your supplies are not connected correctly.

RL in between pin9(square wave out) and ground is 10Kohms.

Look at figure 1 on page 2 of the document you linked. The output driver is connected to common, and so you can't get -12V swings.

Try connecting a PNP transistor, like a 2n3906. Emitter to +12V, base thru 2.2K resistor to out generator output, collector through a 4.7k resistor to -12V.

BrownOut said:

Look at figure 1 on page 2 of the document you linked. The output driver is connected to common, and so you can't get -12V swings.

Try connecting a PNP transistor, like a 2n3906. Emitter to +12V, base thru 2.2K resistor to out generator output, collector through a 4.7k resistor to -12V.

Click to expand...

Hey Brownout, I thought the same thing at first as well, but note there is no common connection on the IC, only VEE and VCC. The chip should be able to output .98 x Vsupply.
https://www.electro-tech-online.com/custompdfs/2010/10/FN2864.pdf

Mikebits said:

Hey Brownout, I thought the same thing at first as well, but note there is no common connection on the IC, only VEE and VCC. The chip should be able to output .98 x Vsupply.
https://www.electro-tech-online.com/custompdfs/2010/10/FN2864-1.pdf

Click to expand...

OK, well I wondered if that graphic was real. It's not.

This guy got a symetrical output about 0 from his 8038. Its only +/- 5v but you ought to be able to tweak the output op-amp to get the +/- 6v you require.

8038 Generator

Seems to me that using an 8038 (vs. a 555) for this is like using a graphing calculator for second-grade math.