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Switching between 3.3v and 5v power output

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vvanders

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switching 5v by 3.3v

I'm currently in the process of trying to build a really simple logic analyzer. As part of this I want to be able to interface with TTL, CMOS and other logic level busses. I found this which should handle my level shifting just fine.

Where I'm running into issues is trying to set the VCCB of the external bus via digital logic. On my board I've got 5v and 3.3v and would like to be able to source VCCB with either one of those voltages set via digital logic(3.3v).

I've thought about using a npn/pnp transistor pair but my transistor knowledge is a little rusty and if I remember right I won't be able to pass a full 5v due to the diode drop. I've also thought about using an analogue switch but I don't think they can source much current, any suggestions?
 

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