Monday, April 9, 2018

Micro-controller Output Protection by Current Limiting

Q1B is the pass or output transistor. R2 sense the output current. Q1A  is the protection transistor which turns on as soon as the voltage across R2 becomes about 0.65 V.
Maximum current = VBE,Q1A / R2 = 0.65 / 33 = 19.7 mA
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General PCB Routing Techniques

For traces that don't need specific impedance or high current, a 10 mil trace width is fine for the vast majority of low-current analog ...