Why totem pole output should not be tied together

SgtWookie

Joined Jul 17, 2007
22,210
If you tie two totem-pole outputs together, they will "fight to the death" if they are set to different logic levels.

You can use diodes from each output with a pull-up or pull-down resistor, depending on the logic you want.

You can tie open-collector outputs together and use a pull-up resistor to create a wired AND gate.
 

SgtWookie

Joined Jul 17, 2007
22,210
A pull-down resistor has one end connected to the low voltage in the circuit; in the case of TTL and CMOS, that is usually ground or Vss.

A pull-up resistor has one end connected to +V, Vcc or Vdd.
 
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