Since 2002 a wide range of current-mode detectors with integrated CMOS OpAmp instead of a JFET source follower has been brought on the market.
Dual channel detectors like the LIM-252 from InfraTec are needed to measure gases. Often, in an optical bench it is necessary to measure two gases at the same time (e.g. CO2 and methane with a reference).
Dual channel pyroelectric infrared detectors (Channel1 = sample gas, and Channel2 = optical reference) are used in sensor modules of many manufactures that build NDIR Gas analyzers. The 4-pin TO39 package in which the Pyroelectric chips are integrated, along with JFETs and high Ohm resistors is a standard.
the “SENSOR Innovation Prize 2008” of the AMA Fachverband für Sensorik e.V. (AMA Special Association for Sensor Technology, non-profit) in Nuremberg on occasion of the SENSOR+TEST fair.