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I stumbled over the circuit in the related question which accroding to the explanation and my understanding implements a comparator by means of two PNP transistors to pull the gate of the P-channels MOSFET.

I would like adapt the circuit select between multiple voltages sources of in the range of 4.5V - 24V like this:

schematic

simulate this circuit – Schematic created using CircuitLab

My issue is that is seems that when the input voltages differ largely like 5V at input 1 and 24V at input 2, the emitter-base voltage of Q2 becomes quite large, exceeding the maximum rating of the BJT. Is this understanding correct?

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  • \$\begingroup\$ check the answer to this question \$\endgroup\$ – next-hack Oct 23 '17 at 10:36
  • \$\begingroup\$ What do you mean "select between multiple sources?" Do you mean to select the highest voltage of them? Or will there only be one of them active at a time? \$\endgroup\$ – jonk Oct 23 '17 at 17:46
  • \$\begingroup\$ I mean to select the highest of two which can be active at the same time \$\endgroup\$ – Arne Oct 23 '17 at 18:25

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