Dual Transistor Inverting Tri-State Buffer Example
Fig. 1

Transistor Output Inverting Tri-State Buffer


This circuit is identical to Transistor Output Non-Inverting Tri-State Switch other than the placement of a single inverter.

Again this is a 5-volt TTL circuit but would be identical if using CMOS gates and a higher voltage up to 15-volts.

The problem becomes connecting to a 5-volt microcontroller. One must use some kind of logic voltage shift circuit.

See examples at Optocouplers for TTL-CMOS Logic Level Shifting.

Tri-State inverter truth table.
Fig. 2 Tri-State inverter truth table.

Using NAND-NOR to create AND, OR gates.
Fig. 3 Using NAND-NOR to create AND, OR gates.

H-bridge motor control based on tri-state switches.
Fig. 4 H-bridge motor control based on tri-state switches.

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