SN74AS21 Dual 4-Input Positive-AND Gates Texas Instruments SN74AS21/SN74ALS21 Dual 4-Input Positive-AND Gates perform the Boolean function Y = A + B + C + D in positive logic. These devices contain two independent 4-input positive-AND gates. These devices have an operating voltage range of 4.5V to 5.5V and a low power consumption of 20μA. The SN74ALS21A and SN74AS21 are characterized for operation from 0°C to 70°C.