DESIGN RULES FOR AN INTEGRATABLE LOW-POWER AMPLIFIER FILTER COMBINATION/

In this paper design rules for a circuit topology in which there is an inseparable combination of an amplifier and a filter characteristic, are presented. By intentionally using the capacitance of an already pr esent input sensor for the filtering, the total required integrated ca pacitance is much less than that in circuits, which have a separately designed amplifier and filter function. Consequently, it is possible t o have the advantage of a better integratability. Moreover, less compl exity in the design is achieved. The presented circuit shows a current -to-voltage conversion and an inherently controllable second-order low -pass filter characteristic. A discrete realization has been designed to test the circuit. This circuit operates down to a 1 V supply voltag e and the transfer shows a 1.8 M Omega current-to-voltage conversion w ith a bandwidth of 6 kHz. Measurement results of this circuit show tha t a 63 dB dynamic range can be achieved with a total required integrat ed capacitance of only 31 pF.