M74HCT138B1R

The M74HCT138B1R from STMicroelectronics is a high-speed CMOS 3-to-8 line decoder fabricated using silicon gate C2MOS technology. This device features a typical propagation delay of 16ns at 4.5V supply and low power dissipation with a maximum quiescent current of 4μA at 25°C.

With three binary select inputs (A, B, and C), it determines which one of the eight outputs goes low when enabled. The decoding function is inhibited, and all outputs go high if the G1 enable input is held low or either G2A or G2B enable inputs are held high. Three enable inputs are provided for easy cascade connection and use in address decoders for memory systems.

All inputs are equipped with protection circuits against static discharge and transient excess voltage. The M74HCT138B1R is compatible with TTL outputs, offering a high-level input voltage (VIH) of 2V (min) and a low-level input voltage (VIL) of 0.8V (max). It has symmetrical output impedance with |IOH| = IOL = 4mA (min) and balanced propagation delays (tPLH ≅ tPHL).

This decoder is housed in a 16-DIP (Dual In-line Package) with a through-hole mounting type. It operates over a temperature range of -55°C to 125°C and requires a single supply voltage between 4.5V and 5.5V.