Ultra-low noise high bandwidth interface circuit for singlephoton readout of photodetectors

摘要

An ultra-low noise, high gain interface circuit for single-photon readout of known photodetectors from the x-ray to long IR bands at video frame rates. The detector current modulate's a load FET's gate-to-source voltage, which in turn modulates the gate-to-source voltage of a gain FET thereby producing a signal current that is an amplified facsimile of the detector current. The load FET's gate-to-source voltage is connected in the negative feedback loop of a low noise, high gain amplifier. This effectively reduces the resistance seen by the photodetector by the gain of the amplifier thereby reducing the interface circuit's RC time constant by the same amount. Because the amplifier pins the load FET's gate voltage for a given flux level, the load FET's 1/f noise is transferred to the amplifier thereby enabling single-photon readout sensitivity.