Electronic – Why does the crystal oscillator spike so much

frequency-measurementoscillatoroscilloscope

I just got a new oscilloscope (Rigol DS1102E) and I'm new to EE in general.

One of the first things I put on the scope was my 3.579Mhz "TKD" crystal oscillator.

What I didn't expect was the spike on each rising and falling edge (hope I said that correctly).

If you look at the attached picture, you will see what I mean.

3.579Mhz spikes

So, what is that all about? I'm building an audio circuit that uses the NTSC frequency to drive an SN76489. The IC uses the frequency to generate square waves for audio so while my circuit sounds "good enough", seems like spikes like that would cause issues later on?

I don't have any resistors or capacitors on my circuit. Just the OSC out to the CLK pin of the IC.

Also, what's the deal with the scope reporting ~3.597Mhz? It seems to fluctuate in the 3.56 – 3.59 range. However, when I put a 1Mhz crystal on the scope, it shows a nice 1.000Mhz frequency.

Best Answer

Most important thing is to compensate your Oscilloscope probe. This may account for the overshoot. - - - Second, Conner Wolf is correct in the ground lead of the probe. I don't know how many times my technicians had problems, and I simply gave them a shorter ground clip lead and magically the ringing disappeared.

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