Programmable multi-gain current amplifier

A programmable multi-gain current amplifier circuit, comprising:

• a complementary metal oxide semiconductor (CMOS) current amplifier having an X terminal, and a first unity gain differential output port Z;
• a first metal oxide semiconductor (MOS) transistor and a second MOS transistor arranged in said programmable multi-gain current amplifier circuit in combination with a third MOS transistor and a fourth MOS transistor, said circuit arrangement producing a negative feedback driving said X terminal to approximately zero volts, wherein constant currents of said second MOS transistor and said fourth MOS transistor flow into said third MOS transistor;
• a current folding output stage formed by a fifth MOS transistor arranged in said programmable multi-gain current amplifier circuit with said first, second, third and fourth MOS transistors, said third MOS transistor being source-coupled with said fifth MOS transistor to form a first differential pair in which an input current ix is conveyed from said input port X to said output port Z;
• means for biasing said third MOS transistor and said fifth MOS transistor with a constant tail current to provide the unity gain in which an output current iZ is equal to said input current ix;
• a second differential pair of a sixth MOS transistor and a seventh MOS transistor connected in parallel with said third MOS transistor and said fifth MOS transistor;
• and
• means for biasing said sixth MOS transistor and said seventh MOS transistor with variable tail currents to provide programmable gains at second and third differential current output ports, said second differential pair and said first differential pair being biased with different tail currents, and second and third current output gains being programmed responsive to adjustment of said variable tail currents.