Photodarlingtons are still produced by Clairex, but only on a custom-device basis. The demand for these sensors has decreased over the years as other options have become available, but not yet dropped to zero. These devices start as photodiodes, but that small light current is fed to the base of a Darlington-connect transistor pair, resulting in light currents that are increased essentially by a factor of hFE2 – a significant increase in light current, but compromised both by lower response speeds and higher leakage currents as a result of base-collector leakage being multiplied by hFE2. Room temperature leakage is generally about the same as for a phototransistor, but increases significantly with increasing temperature.

Contact Clairex for your photodarlingtons needs; the information immediately below and the data sheets referenced are for information only. Photodarlingtons are sold by Clairex only as custom parts.

Part (1)
at Ee (2)
V (min)
qHP (4)
deg. (typ)
ID (5)
nA (max)


  1. Click on a part number for datasheet.
  2. The radiation source is a 940nm IRED. VCE=5V.
  3. Measured at IC=100mA.
  4. Acceptance angle at half power points.
  5. Measured under dark conditions, VCE=10V.
  6. A dark condition exists when further irradiation shielding does not reduce ID