| Electronics > Beginners |
| Current clamp oscillating at 50MHz |
| (1/1) |
| ocset:
We have a DALI power bus comprising a 15mA current clamp in a 15V rail. (as in attached schematic) As a test, I turned on the transistor, Q4. When I clipped a scope probe (or even a TA041 diff probe ) across the 82R resistor, I sometimes saw a 50MHz sinusoidal oscillation across this 82R resistor, of about 250mV pk2pk. Sometimes I have to grab and release the ends of the probe to “start the oscillation off”. We want to stop this oscillation. Do you agree that a good way to damp out this oscillation is to put an RC series circuit from Collector to base of Q3? ( Values of 10n, 10R) I did this in the lab and it certainly put an end to the oscillation, though we wonder if there is a better way to stop it? NXJ1S1215 datasheet: https://power.murata.com/data/power/ncl/kdc_nxj1.pdf TLV431 datasheet: https://www.diodes.com/assets/Datasheets/TLV431.pdf FMMT491A datasheet: https://www.diodes.com/assets/Datasheets/FMMT491A.pdf |
| Wolfgang:
... another way would be a resistor between the sense input of the TLV431 and the current sense resistor (say, 1K), plus a small cap between the anode of the TLV431 and the sense input (try a few 100pF). |
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