Charge-transfer coded-voltage generator for use in analog-digital coders and decoders

Claim 1

A charge-transfer coded-voltage generator for generating the voltages V.sub.R,V.sub.Ri =a.sub.o V.sub.R +a.sub.1 ·V.sub.R /2+a.sub.2 ·V.sub.R /2.sup.2 + . . . +a.sub.i-1 ·V.sub.R /2.sup.i-1 +V.sub.R /2.sup.i, where V R is a reference voltage and where i=1 . . . n and in which said voltages make it possible by comparison with a voltage V x to determine by successive approximations the coefficients a o . . . a n which are equal to 0 or to 1 and such that V x =a o V R +a 1 ·V R /2+a 2 ·V R /2 2 . . . +a i V R /2 i + . . . +a n ·V R /2 n or alternatively for generating the voltage V x =a o V R +a 1 ·V R /2+a 2 ·V R /2 2 + . . . +a i ·V R /2 i + . . . +a n ·V R /2 n in the event that the coefficients a o . . . a n are known, wherein said generator is constituted by a charge-transfer device comprising an alternate arrangement of storage gates and transfer gates together with: a diode D e placed at one end of the active region in which transfer and storage of charges take place, the function of said diode being to inject a reference quantity of charges 2Q R at the beginning of processing of each sample V x or of each series a o . . . a n as well as to effect removal of surplus charges during the processing operation; an insulating diffusion which divides into two equal parts the charges originating from a storage gate G o located near the diode D e and which divides the active region into two parallel channels downstream of the gate G o ; in one channel, a storage gate G 2 beneath which the quantities of charges Q R , Q R /2 . . . Q R /2 i . . . are stored by successive two-trip traversals between gates G o and G 2 ; in the other channel, three storage gates G 1 , G 3 and G 4 , the quantity of charges Q R /2 i stored beneath gate G 1 and originating from gate G o being transferred beneath said gate G o and then removed beneath the diode D e when a i is zero in respect of i=0 . . . n and being transferred beneath gate G 3 when a i is equal to 1; when the coefficients a o . . . a n are unknown, a charge-reading device connected to gates G 2 and G 4 and adapted to generate the reference voltage V R at the time of transfer of the quantity of charges Q R beneath gate G 2 , thus permitting determination of a o by comparison of the voltage V R with the voltage V x , then to generate V R1 =a o V R +V R /2 at the time of transfer of the quantity Q R /2 beneath gate G 2 and, if a o =1, at the time of any subsequent transfer of Q R from gate G 3 to gate G 4 , thus permitting determination of a 1 by comparison of the voltage V R1 with the voltage V x , and so on until generation of V Rn and determination of a n or, when the coefficients a o . . . a n are known, a charge-reading device connected to the gate G 4 for generating the voltage V x by transfer of charges from gate G 3 to gate G 4 when the n coefficients of V x have been processed.