Identifying a component: diode or transistor?


Joined Jan 28, 2017
Looks like a SOT-23 Switching Diode I am not 100% sure however looks like it to me... I am sure someone will have better info then that...



Joined Mar 31, 2012
What is the purpose of the third leg of a switching diode? D4 seems to have all pins connected (not sure about D5 and D3).
Depends on the application, of which there are many.

One common use for series-connected diodes is to provide supply rail clamps for signals.

Your signal is connected to the junction of the two diodes. The cathode of one diode is then connected to the positive rail while the anode of the other is connected to the negative rail. If the signal goes more than a diode-voltage drop outside the rails, the appropriate diode is forward biased and clamps the signal line to that voltage.