Continuously tuning a transconductance. Coupling a degeneration resistance
from a first source of a first transistor in a differential pair of transistors
to a second source of a second transistor in the differential pair of transistors.
Applying a second variable degeneration resistance in parallel to the first degeneration
resistance in response to the application of a first variable control voltage.
And applying a third variable degeneration resistance in parallel to the first
degeneration resistance and the second degeneration resistance in response to the
application of a second variable control voltage having a fixed voltage offset
from the first variable control voltage.