Transconductor stage

An integrated circuit transconductor stage, comprising:

• first and second differential cells, each comprising
• first and second transistors having respective first current-carrying terminals thereof connected in common, and
• a respective current generator connected to provide a fixed current to the connection of said first current-carrying terminals;
• each said first transistor having a respective control terminal connected to provide a respective input connection;
• both said second transistors having respective control terminals thereof connected together;
• wherein said second transistors have device dimensions which provide higher gain than said first transistors;
• said first transistor of said first cell, and said second transistor of said second cell, having respective second current-carrying terminals thereof jointly connected to provide a first current output;
• and said second transistor of said first cell, and said first transistor of said second cell having respective second current-carrying terminals thereof jointly connected to provide a second current output;
• and further comprising a low-pass biasing network connected to bias said control terminals of said second transistors to the long-term average value of said control terminals of said first transistors;
• whereby said first and second outputs provide a differential signal which generally corresponds to the difference in voltage between said input connections.

An integrated circuit transconductor stage, comprising:

• first and second differential cells, each comprising
• first and second transistors having respective first current-carrying terminals thereof connected in common, said second transistors having device dimensions which provide higher gain than said first transistors;
• and
• a respective current generator connected to provide a fixed current to the connection of said first current-carrying terminals;
• wherein said second transistors have device dimensions which provide higher gain than said first transistors;
• each said first transistor having a respective control terminal connected to provide a respective input connection;
• both said second transistors having respective control terminals thereof jointly connected to a variable bias current supply which provides a variable bias current to dynamically adjust the transconductance of said stage;
• said first transistor of said first cell, and said second transistor of said second cell, having respective second current-carrying terminals thereof jointly connected to provide a first current output;
• and said second transistor of said first cell, and said first transistor of said second cell, having respective second current-carrying terminals thereof jointly connected to provide a second current output;
• whereby said outputs provide a differential signal which generally corresponds to the difference in voltage between said input connections.

An integrated circuit transconductor stage for high-frequency filters operated on a low voltage supply, comprising:

• an input circuit portion having signal inputs;
• and
• a pair of differential cells:
• being connected together and each associated with a corresponding signal input,
• each said cell incorporating at least one pair of transistors having at least a corresponding current-carrying terminal in common;
• each cell comprises a minimal area transistor and a transistor with an area .alpha. times as large, where .alpha.>1;
• each said cell comprising a respective current generator connected to provide a fixed current to said common terminal.

An analog filter circuit, comprising:

• a differential input stage, a differential output stage, and one or more additional differential stages, each comprising:
• first and second differential cells, each comprising
• first and second transistors having respective first current-carrying terminals thereof connected in common, and
• a respective current generator connected to provide a fixed current to the connection of said first current-carrying terminals;
• each said first transistor having a respective control terminal connected to provide a respective input connection;
• both said second transistors having respective control terminals thereof connected together and to a biasing circuit;
• said first transistor of said first cell, and said second transistor of said second cell, having respective second current-carrying terminals thereof jointly connected to provide a first current output;
• and said second transistor of said first cell, and said first transistor of said second cell, having respective second current-carrying terminals thereof jointly connected to provide a second current output;
• said stages being connected together, with one or more passive elements, in a circuit relationship to implement a desired continuous-time filter relationship from said input connections of said input stage to said outputs of said output stage.

A second-order low-pass filter circuit, comprising:

• at least one differential transconductor stage which comprises
• an input circuit portion having signal inputs;
• and
• a pair of differential cells being connected together and each associated with a corresponding signal input,
• each said cell incorporating at least one pair of transistors having at least a corresponding current-carrying terminal in common;
• each said cell comprising a respective current generator connected to provide a fixed current to said common terminal.