Linear low-noise mixer

A mixer comprising:

• first input terminals for a first differential input signal;
• a first current source;
• a first differential pair of transistors coupled to said first input terminals and to said first current statue for dividing current from the first current source between the transistors of the first differential pair in dependence upon said first differential input signal;
• second input terminals for a second differential input signal;
• two output terminals;
• two second differential pairs of transistors coupled to said second input terminals, each of the second differential pairs of transistors having controlled current paths coupled to the output terminals and connected to conduct a current, divided between the transistors of the respective pair of the two second differential pairs in dependence upon said second differential input signal, dependent upon current passed by a respective transistor of the first differential pair of transistors;
• and
• at least one second current source coupled to two junctions each between a respective pair of the two second differential pairs of transistors and said respective transistor of the first differential pair of transistors, for passing current so that total current passed by controlled current paths of the first differential pair of transistors is greater than total current passed by the controlled current paths of the two second differential pairs of transistors.

A mixer comprising:

• at least one first current source;
• at least one second current source;
• a first differential pair of transistors having controlled current paths coupled between the at least one first current source and the at least one second current source and connected to divide current passed by the at least one first current source between said controlled current paths in dependence upon a first differential input signal supplied to the first differential pair of transistors;
• two second differential pairs of transistors, each pair of the two second differential pairs of transistors having controlled current paths coupled to a respective junction between a respective transistor of the first differential pair of transistors and the at least one second current source and being connected to conduct current divided between the transistors of the respective pair of the two second differential pairs of transistors in dependence upon a second differential input signal supplied to the two second differential pairs of transistors, total current passed by the controlled current paths of the two second differential pairs of transistors being less than total current passed by the controlled current paths of the first differential pair of transistors;
• and
• output terminals coupled to the controlled current paths of the two second differential pairs of transistors for providing an output signal comprising a product of the first and second differential input signals.