Linear interpolation circuit

A method of generating a plurality of precision currents according to claim I further comprising the steps of:

• demanding an incrementally larger input current from the network at the first control terminal;
• demanding an incrementally smaller input current from the network at the second control terminal;
• shunting current from the network to the first control terminal in an amount equal to the change in current demanded at the first control terminal wherein a corresponding reduction in current in a first network leg is produced;
• and
• shunting current from the network to a second leg in the network in an amount equal to the change in current demanded at the second terminal wherein a corresponding increase in current in a second network leg is produced.

An interpolation circuit for providing bias currents to transconductance amplifiers in a variable gain amplifier, the interpolation circuit comprising:

• a network having a plurality of parallel legs for supplying a precision current, each leg having a current source and a load connected in series;
• first and second control terminals coupled to the network;
• a first shunting diode coupled between each pair of adjacent legs to conduct current in a first direction;
• a second shunting diode coupled between each pair of adjacent legs to conduct current in a second direction;
• and
• means coupled to the loads for providing a bias current to a corresponding transconductance amplifier responsive to a current in the corresponding load.

An interpolation circuit comprising:

• a network having a plurality of parallel legs for supplying a precision current, each leg having a current source coupled thereto;
• first and second control terminals coupled to the network;
• means for shunting current from the network to the first and second control terminals responsive to an input current demand at the first and second control terminals;
• and
• means for producing a linearly interpolated current in one or more legs of the network responsive to the shunting current.

A continuously variable amplifier comprising:

• an attenuation circuit having a pair of input terminals for receiving an input signal, a plurality of taps for providing successively attenuated versions of the input signal, and a common terminal for providing a common output signal;
• a plurality of transconductance stages, each transconductance stage having a first input coupled to a corresponding tap, a second input coupled to the common terminal, an output terminal, and a bias terminal for receiving a bias current;
• an output amplifier having an input terminal having the output terminals of the transconductance stages coupled thereto and an output terminal for providing an output signal;
• and
• a linear interpolation circuit having a plurality of bias current supplying terminals and first and second control terminals for receiving a pair of complementary scanning input currents, each bias current supplying terminal coupled to a bias terminal of a corresponding transconductance stage for supplying a linearly interpolated bias current thereto responsive to the complementary scanning input currents.