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...
**broken link removed**
Thank you
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...
**broken link removed**
Thank you