XR 2206 Question

Good sines can only come from a good triangle, so the chip must be working OK. Fault must be due to loading on the triangle pin. john

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I had no load (only X10 scope probe) on the output, so I tried a 1K load, it only reduced the output by about half, it didn't improve the waveform. Mike

problem?

working

Looks like the chip's knackered :( john

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I have a second chip, I tried that one and have the same poor signal. Mike

Mike,

I've never seen a 2206 do that. Are you powering the 2206 with a split or a single ended supply? Also, a schematic it would be useful for us in trying to help you.

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James T. White

What value have you got for R3 (resistor connected to pin3 on the chip)?. The triangle has typically 2.5* the p-p voltage of the sine output, and you need to reduce R3, so it does not swing beyond 6vp-p, or it'll clip as you are seeing.

Best Wishes

I'm using a 50k fixed resistor to pin 3, this runs from the voltage divider that provides 1/2 vcc to the 50k resistor. I'm using 12v for the vcc and the triangle is 7.5vpp the sine is 5.9vpp. I see the spec sheet says I should have 3vpp sine with the 50k resistor and that would mean about 8vpp for the triangle.

I'm using the circuit on page 8. C=.47uf and R=100k pot. The voltage divider voltage is dead on 1/2vcc, I'll put a variable resistor in place of the 50k and see how that affects the triangle. The amplitude ratio is off between the sine and triangle "hmm". I hope to get some more time this evening to look at it. Thanks, Mike

I should put a load on the output. What is a proper load resistance? That would probably bring my sine output to the proper level! Mike Mike

The specified maximum output swing for the triangle wave, is 6v...

That resistor value is too high. Look at figure 3 in the data sheet. Notice that the triangle wave amplitude goes off the top of the graph at about 44K. You need to be below 40K for the triangle to reliably not clip.

Best Wishes

Yes, I installed a variable resistor as R3 and started reducing the value, the triangle didn't look good until I hit 17k. This value limits my sine output to 2vpp, a little less than I wanted, but I can work with it. Thanks Mike