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Infra Red Lamp IR-50 Series


 The IR-50 range of broadband infra red lamps is based around a very low thermal mass diamond-like carbon thin film element. Due to the low thermal mass, the infra red lamp can be pulsed at frequencies up to 100Hz with good modulation depth, or contrast between the on and off states. It is therefore suitable for use with quantum detectors like photoconductive PbS and PbSe, which otherwise would require a chopper to avoid excess low frequency "flicker" (1/f) noise.

 This lamp is significantly better, watt for watt and Hz for Hz, than any competing non-mechanical modulation that technology offers. This new lamp has an active area of approximately 2.9 mm² and is supplied in a TO-5 style package. The normal working range is 500° to 750° C with peak short term heating up to 850° C possible. Calculated lifetime is approximately three years at 600°C.

 Three families of parts are available in this range though both use the same element as the emitting infra red lamp.

 Please note that over driving or contact with the thin film will cause these devices to fail.


 Standard IR-50 giving a wide output beam.


Ordering Information


 Lamp mounted in TO5 style can (as above).


 Lamp mounted in TO5 style can with sapphire window.


 Lamp mounted in TO5 case base but without the top cap.


 The addition of a parabolic reflector, collimates the output beam giving a narrow output beam with greater intensity.



Ordering Information


 Lamp mounted in parabolic reflector (no window).


 As per the IR-55 but with a smaller parabolic reflector allowing operation in a smaller envelope. 9.1mm x 10.2mm diameter.

Ordering Information


 Lamp mounted in parabolic reflector (no window).

Operating Specifications

IR-50, IR-55 and IR-56


6.4 Volts (AC or DC)



Resistance in the Hot state*:

50 ohms


135 mA


0.9 Watts

Cooling Time Constant:


Heating Time Constant:

35 ms

Modulation Depth:

50% at 63 Hz, 50% Duty Cycle

Active area:

1.7mm x 1.7mm


6+ months at 750°C 10Hz 50% Duty Cycle, typical
3+ years at 600°C 10Hz 50% Duty Cycle, typical
8+ years at 450°C 10Hz 50% Duty Cycle, typical
(constant operation is approximately half these figures).

* Measured at 5 Hz frequency, 50% duty cycle.

Modulation Depth

IR55 Increase in On-axis Output

IR50 and IR55 Max Frequency Relative to Competitors

IR-55 Drawing

infrared source IR 50 / 55 Current vs Volts and Power vs Volts

infrared source IR 50 / 55 Temperature vs Volts

Operation above the normal operating point of 750°C and 6.4V will severely reduce the lifetime of the part. Approaching the upper limit runs the risk of blowing the thin film element. Long term operation at 850° is not recommended.

Operating Guidelines

The IR-50 Series utilises a thin thermoresistive conducting film of amorphous (diamond-like) carbon. Infrared radiation is the result of heating this film by passing an electric current through it.

Either a constant voltage or a constant current power source is suitable for driving these parts, however it is the temperature of the source that is important.

The maximum temperature of the film should not exceed 750°C in continuous operation. A faint red luminescence of the film is observed during continuous operation at temperatures near 750°C. Short term heating up to 850°C is possible but will reduce the lifetime of the unit.

The specifications shown below assume an infrared source operating without a radiator and at ambient temperature and pressure. Operation with a radiator will cause the part to cool and hence the temperature of the part will drop and the drive voltage will need to be increased to compensate. Operating in an enclosed space or a high ambient temperature will generally cause the part to overheat and the drive voltage will need to be reduced to compensate.

The IR-50 Series is the perfect solution for an application that requires fast electrical modulation. However, it can also be used in a steady state (DC) mode. In applications where steady state power is used (or if used with electrical modulation but with a duty cycle of greater than 50%), it is recommended that the nominal input power specifications not be exceeded in order to avoid overheating of the membrane. On the other hand, by reducing the length of the heating pulse or by increasing the frequency of modulation, the membrane will not have sufficient time to reach 750°C. In this case, the pulsed power can be increased to allow 750°C to be maintained. The chart below shows the factor by which the voltage can be increased as frequency is increased. This chart assumes a 50% duty cycle. Use this Voltage Ratio to maintain constant temperature.

infrared source IR 50 / 55 voltage increase for high frequencies

Using a 50% duty cycle and the appropriate power factor as determined above, a 50% modulation depth is achievable at modulation frequencies of more than 60 hertz. This modulation depth can be achieved at even higher frequencies (more than 100 hertz) if a 25% duty cycle were used along with a correspondingly higher power factor (sufficient to maintain the membrane temperature at 750°C). Please contact us for assistance in determining the proper power factor for the duty cycle to be used in your application.

Please note that over driving or contact with the thin film will cause these devices to fail.

Spectral Radiance

Blackbody Spectral Radiance Spectral radiance output for a perfect black body of various temperatures. The IR-50 and IR-55 produces approximately 80% of these figures in the 1µm to 22µm range.

Useful Documents


Infra Red Source Series 50 Data Sheet - pdf (161K)


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