question about sn7407n

qsd said:

Hi,
I built classic Tait style PIC programmer. Everything was ok until I decided to make development board from it. The problem is than then I turn off Vdd to the 7407 IC, it seems that it still can sink current, because MCLR PNP transistor is open. Is this possible(with good design and IC)? Or maybe I have bad IC? Looking at the schematic of one gate of IC, I don't see a way how can that last transistor be open without Vcc... Input isn't connected to anything, and there are pullup on output...

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qsd said:

Thanks for answer.

I thought that if I would turn off the IC, there autimatically won't be any signal from PC , so anything left from programmer would be only pull ups on RB6 and RB7... And I would need only simple small DPDT switch...
And now I got one more question... Would it work if I turn off both Vdd and ground? And would it be ok if I turn off only ground for crystal oscillator(F1100E)?
Thats because I don't have space on my PCB for any other switches

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