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 the upper frequency is limited to values less than 50 Hz often. For such amplifiers conversion factors between 10^7 V/W and 10^10 V/W can be realized.

The amplification can be set by a 4-step switch: e.g. 10^7 ...  10^10 V/A ; the bandwidth is fixed* to e.g. 50Hz or 250 Hz. The detection limit depends on the amplification, the bandwidth and detector diameter.

*please ask if you need other parameters