The ACPL-K370 and ACPL-K376 are voltage/current threshold detection optocouplers. The ACPL-K376 is a low-current version of the ACPL-K370. To obtain lower current operation, the ACPL-K376 uses a high-efficiency AlGaAs LED which provides higher light output at lower drive currents. The devices utilize threshold sensing input buffer ICs which permit control of threshold levels over a wide range of input voltages with a single external resistor. The input buffer incorporates several features: hysteresis for extra noise immunity and switching immunity, a diode bridge for easy use with ac input signals, and internal clamping diodes to protect the buffer and LED from a wide range of over-voltage and over-current transients. Because threshold sensing is done prior to driving the LED, variations in optical coupling from the LED to the detector will have no effect on the threshold levels. The ACPL-K370's input buffer IC has a nominal turn on threshold of 3.8 volts (VTH+) and 2.77 mA (ITH+). The buffer IC for the ACPL-K376 was designed to permit a lower input current. The nominal turn on threshold for the ACPL-K376 is 3.8 volts (VTH+) and 1.32 mA (ITH+), which reduces power dissipation by 52%. The high gain output stage features an open collector output providing both TTL compatible saturation voltages and CMOS compatible breakdown voltages. By combining several unique functions in a single package, the user is provided with an ideal component for industrial control computer input boards and other applications where a predetermined input threshold level is desirable.