Differential amplifier with variable neutralization
AssigneeTexas Instruments Incorporated
InventorsKrishnanshu Dandu, Brian P. Ginsburg
Life of this patent
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Abstract
Disclosed examples include differential amplifier circuits and variable neutralization circuits for providing an adjustable neutralization impedance between an amplifier input node and an amplifier output node, including neutralization impedance T circuits with first and second impedance elements in series between the amplifier input and output, and a third impedance element, including a first terminal connected to a node between the first and second impedance elements, and a second terminal connected to a transistor. The transistor operates according to a control signal to control the neutralization impedance between the amplifier input node and the amplifier output node.
Claims20
An amplifier circuit comprising:
- an input stage including first and second transistors;
- an output stage;
- an adjustable impedance stage coupled between the input stage and the output stage, wherein the adjustable impedance stage has an impedance, the adjustable impedance stage including a first adjustable impedance circuit having a third transistor, and first capacitive circuitry coupled to the first transistor, and a second adjustable impedance circuit having a fourth transistor, and second capacitive circuitry coupled to the second transistor;
- and
- a controller that includes a control input and a control output, wherein the controller is coupled to the adjustable impedance stage and configured to adjust the impedance based on the control input.
An amplifier circuit comprising:
- a differential input that includes a first amplifier input configured to receive a first component of a differential input signal and a second amplifier input configured to receive a second component of the differential input signal;
- a differential output that includes a first amplifier output and a second amplifier output;
- a first impedance element coupled between the first amplifier input and the first amplifier output;
- a first impedance control transistor coupled to the first impedance element;
- a second impedance element coupled between the second amplifier input and the first amplifier output,
- a second impedance control transistor coupled to the second impedance element;
- a control circuit that includes a control input a first output and a second output,
- wherein the first output is coupled to the first impedance control transistor to provide a first control signal based on the control input, and the second output is coupled to the second impedance control transistor to provide a second control signal based on the control input.
An amplifier circuit comprising:
- a differential input that includes a first transistor having first and second terminals and a control terminal forming a first amplifier input and a second transistor having first and second terminals and a control terminal forming a second amplifier input, the second current terminals of the first and second transistors coupled together;
- a differential output that includes a first amplifier output and a second amplifier output;
- a neutralization circuit that includes:
- a first input configured to receive a first voltage control signal;
- first capacitive circuitry coupled between the first amplifier input and the first amplifier output, wherein the first capacitive circuitry is responsive to the first voltage control signal;
- and
- a third transistor having a control terminal coupled to the first input and a another terminal coupled to the first capacitive circuitry;
- and
- a control circuit that includes a first output coupled to the first input of the neutralization circuit to provide the first voltage control signal.
Dependencies are inferred from the claim text.