read out power consumption by a factor of 2 this occurs because the number of required buffers is divided by 2 with power consumption decreased by the same factor this is particularly important for the active line memory circuits because column buffers will be the main power consumer this invention reduces in column matching error to zero when using column buffers having only one buffer per column eliminates matching errors this invention reduces column to column matching error by a factor of 2 when using column buffers by reducing the number of devices to match from column to column let c mem be the column capacitor 601 602 etc and c par be the parasitic capacitance of the bus assume a typical line memory gain a lm 0 5 chip output 614 at time 717 contains 50 of the original v n signal and 50 of the v ref reference the same applies to the second sample taken at time 717 v out a lm v ns 1 u2212 a lm v ref 9 when the cds subtracts these two samples the v ref portion cancels out leaving only v cds a lm v n u2212 v ns a lmvs 10 thus the present invention obtains the image signal v s without using a differential amplifier a delay between the n and ns outputs causes the cds to do all the calculation fig8 illustrates this invention implemented in an active line memory.