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To verify that I've soldered a pin correctly, I took a scope capture and noticed there is a ~560mV high bias. This is on an old motherboard where one or more capacitors could be bad. What is a good way to bring this clock signal into a digital circuit?

low pin count bus clock pin scope capture

Jacob P
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  • Into what circuit? Start with AC coupling (i.e. via a capacitor) and then you may need to re-bias and/or amplify to interface with whatever the circuit is. – user253751 Jul 15 '22 at 18:54
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    If this is supposed to be a digital signal, then you may have a measurement problem. What is the bandwidth of your scope? Also, the scope will only achieve this bandwidth with a proper probe, used correctly. – Mattman944 Jul 15 '22 at 19:24
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    This questions says so little when it should detail so much, I'm afraid. Please edit your question and greatly improve it with details and explanations of what you are doing on what and why. As it is, it's impossible to answer so VTC. – TonyM Jul 15 '22 at 19:27
  • Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. – Community Jul 15 '22 at 19:52
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    What are you measuring? A leg of a crystal in an oscillator, or digital square wave clock? What do you expect to see? Because if you are using a 1x probe, you won't see it. – Justme Jul 15 '22 at 20:25
  • The scope is advertised at 200MHz with 1Giga sample per second. – Jacob P Aug 01 '22 at 15:27

1 Answers1

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I'm a mind reader, so tell me if I am correct in saying.

You are measuring using a bandwidth limited method using a 1x probe of a 33 MHz logic signal with a scope that cannot see the harmonics of the square wave so it appears attenuated and sinusoidal.

The mean voltage is around 1.3Vdc which means (no pun intended) it is suitable for any logic family that is 74HCT or 3V logic family.

In other words this waveform is normal but not accurate as a squarewave.

What is a good way to bring this clock signal into a digital circuit?

  1. Consider 24 AWG twisted pair , UTP or STP wire and bring Vdd and Vss as well.
Tony Stewart EE75
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