Multiple emitter transistor

A multiple-emitter transistor is a specialized bipolar transistor mostly used at the inputs of TTL NAND logic gates. Input signals are applied to the emitters. Collector current stops flowing only if all emitters are driven by the logical low voltage, thus performing a NAND logical operation using a single transistor. Multiple-emitter transistors replace diodes of DTL and allow reduction of switching time and power dissipation.