Methods and apparatus to improve difference amplifiers

A device comprising:

• a first input;
• a second input;
• an input stage coupled to the first input and the second input, the input stage including:
• a first transistor including a first control terminal, a first current terminal, and a second current terminal;
• a second transistor including a second control terminal, a third current terminal, and a fourth current terminal;
• a differential amplifier including:
• a supply input coupled;
• an inverting input coupled to the first current terminal;
• a non-inverting input coupled to the third current terminal;
• a first output coupled to the first control terminal;
• and
• a second output coupled to the second control terminal;
• a first resistor having a first terminal coupled to the supply input and a second terminal coupled to the first input;
• a second resistor having a first terminal coupled to the supply input and the first terminal of the first resistor and a second terminal coupled to the second input;
• a third resistor coupled between the inverting input and the first input;
• and
• a fourth resistor coupled between the non-inverting input and the second input;
• and
• a differential-to-single ended converter coupled to the second current terminal and the fourth current terminal.

A difference amplifier having a first reference terminal operable to be coupled to a first terminal of a first resistor and having a second reference terminal operable to be coupled to a second terminal of the first resistor, the difference amplifier comprising:

• an input stage coupled to the first reference terminal and the second reference terminal, the input stage including:
• a floating differential amplifier coupled to the first reference terminal and the second reference terminal, the floating differential amplifier configured to convert a differential voltage across the first resistor to a differential output;
• a first transistor coupled to the floating differential amplifier, the first transistor configured to be controlled by the differential output and pass a first current from the first reference terminal;
• a second transistor coupled to the floating differential amplifier, the second transistor configured to be controlled by the differential output and pass a second current from the second reference terminal;
• a second resistor configured to cause a first intermediate voltage by generating a first voltage drop based on the first current;
• a third resistor configured to cause a second intermediate voltage by generating a second voltage drop based on the second current;
• a fourth resistor coupled between the first reference terminal and a supply input of the floating differential amplifier;
• and
• a fifth resistor coupled between the second reference terminal and the supply input of the floating differential amplifier;
• and
• a differential amplifier configured to convert a differential voltage based on a difference between the first intermediate voltage and the second intermediate voltage to a single-ended voltage.

An apparatus comprising:

• a differential amplifier including:
• an inverting input coupled to a first input via a first resistor;
• a non-inverting input coupled to a second input via a second resistor;
• a first supply input coupled to the first input via a third resistor, and the first supply input coupled to the second input via a fourth resistor;
• a second supply input coupled to a current source;
• a non-inverting output;
• an inverting output;
• a substrate layer;
• an N-type buried layer coupled to the first supply input;
• and
• a buried oxide layer coupled between the substrate layer and the N-type buried layer;
• a first transistor including a first control terminal and a first current terminal, the first control terminal coupled to the non-inverting output and the first current terminal coupled to the inverting input;
• and
• a second transistor including a second control terminal and a second current terminal, the second control terminal coupled to the inverting output and the second current terminal coupled to the non-inverting input.

A device comprising:

• a first input;
• a second input;
• an input stage coupled to the first input and the second input, the input stage including:
• a first transistor including a first control terminal, a first current terminal, and a second current terminal;
• a second transistor including a second control terminal, a third current terminal, and a fourth current terminal;
• a differential amplifier including:
• a supply input coupled;
• an inverting input coupled to the first current terminal;
• a non-inverting input coupled to the third current terminal;
• a first output coupled to the first control terminal;
• a second output coupled to the second control terminal;
• a substrate layer;
• an N-type buried layer coupled to the supply input;
• and
• a buried oxide layer coupled between the substrate layer and the N-type buried layer;
• a first resistor coupled between the supply input and the first input;
• a second resistor coupled between the supply input and the second input;
• a third resistor coupled between the inverting input and the first input;
• and
• a fourth resistor coupled between the non-inverting input and the second input;
• and
• a differential-to-single ended converter coupled to the second current terminal and the fourth current terminal.