The HCPL-0370/3700 and HCPL-3760 are voltage/current threshold detection optocouplers. The HCPL-3760 is a low-current version of the HCPL-0370/3700. To obtain lower current operation, the HCPL-3760 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.