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The 267 is used as the main amplifier in DC systems employing photodiode or photomultiplier detectors.
At low frequencies such devices give their best performance when connected to this type of virtual ground input.
The input effectively has zero input impedance and hence no voltage is generated across the device as a result of the photocurrent.
This short circuit operation enhances linearity of detectors and reduces the effect of cable capacitance.
Programmable dual inputs allow the use of pairs of detectors to increase the wavelength range of a scanning system.
Typical examples include pmt/Si, Si/Ge and Si/InGaAs.
| Specification | |
| Transconductance | 10E10V/A to 10E5 V/A |
| Bandwidth | DC to 30Hz |
The 267 is useful in any application where a precise measurement of the current from a photomultiplier or photodiode is required.
The unit is found in systems ranging from simple photometers using a single photodiode to sophisticated spectroradiometers with dual detector.
The schematic shows a typical spectroradiometer using a photomultiplier and indium gallium arsenide photodiode to cover the wavelength from 200nm to 1700nm.
