Output circuit for charge transfer transversal filter

Claim 1

A transversal filter comprising a substrate of semiconductor material of one conductivity type, a first plurality of electrodes insulatingly overlying said substrate, each split into a first and a second part with a gap therebetween, a second plurality of electrodes insulatingly overlying said substrate, each spaced between adjacent electrodes of said first plurality, said first and second pluralities of electrodes forming a plurality of stages of a shift register, means for connecting the first parts of said electrodes of said first plurality to a first conductive line, means for connecting the second parts of said electrodes of first plurality to a second conductive line, means for introducing packets of charge representing successive samples of an analog signal into said shift register, charge clocking means to effect the transfer of charge from storage region to storage region underlying said first and said second pluralities of electrodes including means for applying first and second phase related voltages to said first and second pluralities of electrodes respectively, said first voltage being applied to said first and said second lines, said second voltage having a predetermined periodicity, differential sensing means connected to said first and second lines for detecting a difference in signal on said lines in response to the transfer of charge from storage regions underlying said second plurality of electrodes to storage regions underlying said first plurality of electrodes for obtaining a sum of weighted samples of said analog signal including a high gain differential amplifier having a pair of input terminals and an output terminal, one of said input terminals being an inverting input terminal and the other being a non-inverting terminal, a first capacitor, said inverting terminal connected to said output terminal through said first capacitor and also connected to said first line, said non-inverting terminal connected to said second line, a source of said first phase related voltage, a first and a second charging and isolating means, said connecting said source to said first and second lines respectively to charge each of said lines to substantially the value of said first phase related voltage of said source periodically prior to the transfer of charge into the storage regions underlying said first plurality of electrodes and thereafter isolating said lines from said source, whereby charge periodically transferred from the storage regions underlying said second plurality of electrodes to storage regions underlying said first plurality of electrodes induce different voltages on said lines and causes the voltage of the inverting terminal to follow the voltage of the non-inverting terminal by virtue of the feedback through said first capacitor and a total charge is supplied to said first capacitor which is proportional to the difference in charge delivered to said lines during said transfer of charge, said total charge appearing as a change in voltage at said output terminal.