The 6N139 is a 100kbaud High Speed Optocoupler with low input current and photodiode Darlington output. High common mode transient immunity and very high current ratio together with 5300Vrms insulation are achieved by coupling and LED with an integrated high gain photo detector. Separate pins for the photo diode and output stage enable TTL compatible saturation voltages with high speed operation. Access to the base terminal allows adjustment to the gain bandwidth. It is best suited for low power logic applications involving CMOS and low power TTL.