AND Gate Power - SN74AHC1G09

Anthony Berwin

Other Parts Discussed in Thread: SN74AHC1G09

When Pin 5 (Vcc) of SN74AHC1G09 is low (or connected to ground), what happens when an external high is put on the inputs or the output?

Regards, Anthony

over 13 years ago

0 Edwin Krasser over 13 years ago

Expert 2420 points

If there is no supply your gate will be powered over the signal lines (gate protection diodes at input, bulk diodes at output). But: If you tie Vcc to GND the diodes will be in forward direction to GND, hence you will get some hundred mV at the pins, depending on how strong your signal is (plus a little bit of heat, ...).

Best regards,
Edwin Krasser

0 Anthony Berwin over 13 years ago in reply to Edwin Krasser

Prodigy 250 points

I think you answered my question. Some schematics of the inputs/outputs would be helpful.

I assume the output will look like a pair of anti-parallel diodes. Is this the same as the bulk diodes you are referring to?

0 Edwin Krasser over 13 years ago in reply to Anthony Berwin

Expert 2420 points

Hi!

You should easily find some literature about CMOS schematics on the websites of TI, NXP, ... . Just look for the different CMOS family guides (HC, AHC, LVC, ...).

Best regards,
Edwin Krasser

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AND Gate Power - SN74AHC1G09