Low Input Current, High Gain Optocouplers

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This high gain series optocoupler uses a Light Emitting Diode and an integrated high gain photodetector to provide extremely high current transfer ratio between input and output. Separate pins for the photodiode and output stage result in TTL compatible saturation voltages and high speed operation. Where desired the VCC and VO terminals may be tied together to achieve conventional photodarlington operation. A base access terminal allows a gain bandwidth adjustment to be made.

The 6N138 is designed for use mainly in TTL applications. Current transfer ratio (CTR) is 300% minimum over 0 to 70 degrees C for an LED current of 1.6 mA (1 TTL Unit load). A 300% minimum CTR enables operation with 1 TTL Load using a 2.2 k ohm pull-up resistor.

Selection for lower input current down to 250 mA is available upon request.



  • High Current Transfer Ratio - 2000% Typical
  • Low Input Current Requirements - 0.5 mA
  • TTL Compatible Output - 0.1 V VOL Typical
  • Performance Guaranteed over Temperature 0 degrees C to 70 degrees C
  • Base Access Allows Gain Bandwidth Adjustment
  • High Output Current - 60 mA
  • Safety Approval
UL Recognized - 2500 V rms for 1 Minute and 5000 V rms for 1 Minute (for option 020) per UL 1577
CSA Approved
  • Available in 8-Pin DIP or SOIC-8 Footprint or Widebody Package
  • Options available are:
020 = 5000 Vrms/1 Minute UL Rating Option
300 = Gull Wing Surface Mount Option
500 = Tape and Reel Packaging Option
XXXE = Lead Free Option


  • Ground Isolate Most Logic Families - TTL/TTL, COMS/TTL, CMOS/CMOS, LSTTL/TTL, CMOS/LSTTL
  • Low Input Current Line Receiver
  • EIA RS-232C Line Receiver
  • Telephone Ring Detector
  • 117 V ac Line Voltage Status Indicator - Low Input Power Dissipation
  • Low Power Systems - Ground Isolation

Lifecycle Status


Substance Compliance

  • RoHS
    Pb & Pb-free options available
Specification Value
Lifecycle Active
Distrib. Inventory Yes
RoHS6 Compliant Pb & Pb-free options available
Product Type 100 KBd Darlington Transistor Output
Package 300mil DIP-8
VDD (V) 5
IF Min. (mA) 0.5
CTR Min. (%) 300.0
CTR Max. (%) 2600
Prop Delay (tPLH) Max. (µs) 50.0
Prop Delay (tPHL) Max. (µs) 15.0
CMR (min.) (V/µs) 1000.0
Vcm (V) 10.0
UL Insulation Rating Viso (VRMS) 5000.0
Application Brief1 i
Application Note6 i
Brochures2 i
Data Sheet1 i
FAQs2 i
Obsolescence Notice1 i
Options Data Sheet6 i
Product Change Notice (PCN)18 i
Regulatory Certificate3 i
Reliability Data Sheet5 i
Selection Guide2 i
White Papers3 i
Promotional Material1 i