Digitally controlled current source

A current source for providing a logarithmic output current at an output, comprising:

• a plurality of constant current sources each providing a substantially constant current;
• a current mirror circuit having an input and output each of which are coupled to a respective one of said plurality of current sources and including first and second current conduction paths each of which comprise a plurality of series connected resistors:
• at least two switch means each coupled between respective other ones of said plurality of constant current sources and a selected interconnection between a respective pair of said series connected resistors in said first current conduction path, said at least two switch means being responsive to control signals applied at respective inputs thereof for steering currents to said interconnections;
• and
• an amplifier coupled between said output of said current mirror circuit and an interconnection between two of said plurality of series connected resistors in said second current conduction path and including an output coupled to the output of the current source at which is provided the output current in response to said currents being steered to said current mirror circuit from said at least two switch means.