Biasing for Stacked Circuit Configurations

1 . A circuit for compensating for a difference in biasing currents of a first and second circuit element in a stacked circuit configuration, comprising:

a first biasing source for biasing said first circuit element;

a second biasing source for biasing said second circuit element; and

a current-difference source for generating a difference current that is substantially equal to said difference in said biasing currents of said first and second circuit element;

wherein said current-difference source supplies said difference current to compensate for said difference in said biasing currents of said first and second circuit element.

2 . The circuit of claim 1 wherein said first circuit element is a low noise amplifier and said second circuit element is a mixer.

3 . The circuit of claim 2 wherein said first constant biasing source is a constant g m current source.

4 . The circuit of claim 3 wherein said second constant biasing course is a constant IR current source.

5 . The circuit of claim 1 wherein said current-difference source includes a current-summing note for generating said difference current and a plurality of current mirrors for supplying said difference current to said first circuit element.

6 . The circuit of claim 3 wherein said constant g m current source includes a variable resistor for dynamically compensating for process, temperature and supply variations.

7 . A method of compensating for a difference in biasing currents of a first and second circuit element in a stacked circuit configuration, comprising the steps of:

biasing said first circuit element with a first biasing current;

biasing said second circuit element with a second biasing current;

generating a difference current substantially equal to said difference in said biasing currents of said first and second circuit element; and

supplying said difference current to said first circuit element to compensate for said difference in biasing currents.

8 . The method of claim 7 wherein said first circuit element is a low noise amplifier and said second circuit element is a mixer.

9 . The method of claim 8 wherein said biasing of first circuit element comprises supplying a constant g m current.

10 . The method of claim 9 wherein said biasing of said second circuit element comprises supplying a constant IR current.

11 . The method of claim 7 wherein said step of generating a difference current comprises supplying said first constant current and said second constant current to a current-summing node to generate said difference current.

12 . The method of claim 11 wherein said step of supplying said difference current to said first circuit element comprises mirroring said difference current with a current mirror.

13 . The method of claim 9 wherein said step of supplying a constant g m current comprises tuning a variable resistor to dynamically compensate for process, temperature and supply variations.

14 . A communications apparatus having a transceiver with a first and second circuit element in a stacked circuit configuration, comprising:

means for biasing said first circuit element with a first biasing current;

means for biasing said second circuit element with a second biasing current;

means for generating a difference current substantially equal to the difference between said first and second biasing current; and

means for supplying said difference current to said first circuit element to compensate for said difference in biasing currents.

15 . The communications apparatus of claim 14 wherein said first circuit element is a low noise amplifier and said second circuit element is a mixer.

16 . The communications apparatus of claim 15 wherein said first constant biasing source is a constant g m current source.

17 . The communications apparatus of claim 16 wherein said second constant biasing course is a constant IR current source.

18 . The communications apparatus of claim 14 wherein said current-difference source includes a current-summing note for generating said difference current and a plurality of current mirrors for supplying said difference current to said first circuit element.

19 . The communications apparatus of clam 16 wherein said constant g m current source includes a variable resistor for dynamically compensating for process, temperature and supply variations.