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Current-Preamplifier CPA


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Detectors and Acc.

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The current preamplifier is necessary to realize a power measurement of the incoming radiation. The amplifier consists of an IC as transimpedance amplifier at the input side and two further voltage amplifier stages. There are some additional components for a noise reduction and offset regulation. In praxis the maximum amplification is limited by the cut off-frequency. Highest amplification can only be realized for small frequency intervals. For THz detectors in combination with a chopper often the upper frequency is limited to values less than 50 Hz. For such amplifiers conversion factors between 10 7 V/W and 1010 V/W can be realized.

 The sensitivity of the combination detector and preamplifier is determined by multiplication of the current sensitivity of the detector and the amplification of the current amplifier ( e.g. detector 10-6 A/W and CPA 109 V/A leads to a total sensitivity : 10-6A/W*109 V/A=1000 V/W). The amplification can be set by a switch.

The CPA needs an operating voltage ±15 V from an included separate power supply.


Power supply:    ±15 V

Input connector:    SMA or BNC

Output connector:   BNC

Power connector:  Lemo

The amplification can be set by a 4-step switch: e.g. 107...   1010 V/A ; the bandwidth is fixed* to e.g. 20Hz or 200 Hz. The detection limit depends on the amplification, the bandwidth and detector diameter.

*please ask if you need other parameters