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  • Author Author: kk99
  • Date Created: Date Created
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Experiments with the relaxation oscillator

kk99

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Today, I built a simple relaxation oscillator with the 74HC14 integrated circuit. The purpose of this circuit was to get a reasonably fast rising time pulse generator. Here is measurement from SDS824X HD:
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It is observable a noticeable ringing. For comparison similar measurement done by Analog Discovery 3:
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Update 16.02.2026

I have created a soldered version of this circuit on a prototyping PCB and performed measurements again.

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The first measurement was with an oscilloscope probe connected in the same way as in the case of the usage of a breadboard.

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Still noticeable ringing is observable. So, I have performed once more measurement this time with the usage of a ground spring.

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This time ringing is noticeably smaller. Measured mean rise time: 1.9179 ns is pretty close to this one provided by the manufacturer of the oscilloscope: 1.8 ns.

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  • in reply to DAB

    I think that is due to the usage of a breadboard, which introduces parasitic capacitance and inductance. For example, with a series resistor at the output, the ringing was smaller, but this causes a slight slowdown in edge speed. Probing should be better also (usage of ground spring or direct connection 50 Ohm) I think the best option is to use the PCB with possible short connections and a ground plane.