Differential cascode amplifier
AssigneeXilinx, Inc.
InventorFiras N. Abughazaleh
Life of this patent
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Abstract
A differential amplifier amplifies input signals and includes first and second differential input transistor pairs. The first input pair controls output voltages by adjusting sink currents coupled to the outputs. The second pair of transistors compliments the first pair by dynamically adjusting a current sourced to the outputs. A common mode circuit has also been described that adjusts both the current sourced to the outputs and the sink currents. In one embodiment, the amplifier is fully differential and controls both current source transistors and current sink transistors coupled to the amplifiers outputs.
Claims26
A differential amplifier comprising:
- differential output nodes;
- first and second current sources coupled to the differential output nodes;
- first and second current sinks coupled to the differential output nodes for sinking current from the differential output nodes;
- a first pair of differential input transistors coupled to the first and second current sources to adjust output voltages on the output nodes in response to input signals;
- and
- a second pair of differential input transistors coupled to the first and second current sources to adjust currents provided by the first and second current sources in response to the input signals.
A differential cascode amplifier comprising:
- input connections to receive differential input signals;
- output connections to provide differential output signals;
- first and second current sources coupled to the output connections;
- a first pair of differential input transistors coupled to sink a portion of currents provided by the first and second current sources in response to the input signals;
- and
- a second pair of differential input transistors coupled to adjust currents provided by the first and second current sources in response to the input signals.
A differential cascode amplifier comprising:
- input connections to receive differential input signals;
- output connections to provide differential output signals;
- a first differential circuit coupled to adjust the differential output signals in response to the input signals;
- a second differential circuit coupled to adjust source currents electrically coupled to the output connections in response to the input signals;
- and
- common mode circuitry to adjust a combined current sink of the first differential circuit in response to a common mode voltage of the input signals.
A differential cascode amplifier comprising:
- first and second input connections to receive differential input signals;
- first and second output connections to provide differential output signals;
- output circuitry coupled to the first and second output connections and comprising,
- a first current source transistor electrically coupled to the first output connection,
- a first current sink transistor electrically coupled to the first output connection,
- a second current source transistor electrically coupled to the second output connection, and
- a second current sink transistor electrically coupled to the second output connection;
- differential circuitry coupled to the output circuitry and comprising,
- a first input transistor electrically coupled to the first output connection,
- a second input transistor electrically coupled to the second output connection, and
- a tail current transistor coupled to the first and second input transistors, wherein the first and second input transistors sink current from the first and second current source transistors through the tail current transistor in response to the input signals;
- and
- a dynamic bias circuit coupled to gates of the first and second current source transistors.
A method of operating a differential amplifier circuit comprising:
- providing source currents to first and second differential output connections in response to first and second differential input signals;
- adjusting current levels of the source currents in response to the first and second differential input signals and
- partially steering the source currents in response to the first and second differential input signals.
A method of dynamically adjusting a differential cascode amplifier comprising:
- controlling differential output voltages on output connections in response to differential input voltages using a first pair of differential transistors, wherein the first pair of differential input transistors control current sink paths for sinking a portion of currents provided by current sources coupled to the output connections;
- and
- dynamically adjusting the current sources in response to a second pair of differential input transistors.
Dependencies are inferred from the claim text.