Bidirectional transconductance amplifier

In an apparatus for the analog to digital conversion of an input signal, said input signal being a voltage signal, the apparatus having a plurality of stages for performing the conversion algorithm I.sub.out =2.vertline.I.sub.in .vertline.-I.sub.ref, wherein I.sub.in is the current at the input of a particular stage, I.sub.out is the current at the output of that stage which becomes the I.sub.in to the next stage, and I.sub.ref is a chosen reference current, with each stage of the analog to digital converter apparatus comprising a current rectifier, at least one current mirror having a gain of 2, and a current mirror with said I.sub.ref as an input and said I.sub.out as an output, a transconductance amplifier for taking said input voltage signal and changing it into a related current signal I.sub.in, said transconductance amplifier comprising:

• (a) a resistance means in series with said voltage signal input;
• (b) first and second double output current mirrors, wherein each output of said first double output mirror is connected to a corresponding output of said second double output mirror, and the inputs of said double output current mirrors are connected;
• (c) an operational amplifier with the inverting input connected to ground, the noninverting input connected to said resistance means, and the op amp output connected to the inputs of said first and second double output mirrors,
• wherein first outputs of said first and second double output mirrors are connected to said noninverting input of said operational amplifier, and the second outputs of said first and second double output mirrors are connected to said output current.