XR-8038 square wave generator

[outater]

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

 

[BrownOut]

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.

 

[outater]

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

 

[BrownOut]

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.

 

[Mikebits]

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.

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

 

[BrownOut]

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

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

 

[Jaguarjoe]

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

 

[Dean Huster]

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