An auto-ranging photodiode preamplifier with 114 dB dynamic range

A low noise photodiode preamplifier integrated circuit with auto-ranging gain capability has been designed, fabricated, and tested. When connected to a 25 pF input capacitance, the four-channel device has an input referred noise below 0.5 fC, which is just 3 dB above the minimum kTC noise. The preamp chip is designed to handle a full-scale charge input of 210 pC and has a 114 dB dynamic range. The device achieves a linearity specification of 0.01% of input reading /spl plusmn/0.25 ppm of full scale with a sample period of 1 ms. The chip consumes 135 mW and is 5.8 mm/spl times/7.4 mm in size.