Single-ended input to differential output amplifier with integral two-pole filter

Claim 2

A circuit which receives a single-ended input signal and implements a predetermined transfer function to provide a differential output signal, comprising: an amplifier having first and second input terminals, and first and second output terminals; first circuit means coupled to said amplifier for receiving a reference voltage, said first circuit means implementing a first part of the predetermined transfer function and comprising: a first resistor having a first terminal for receiving said reference voltage, and a second terminal; a second resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said first output terminal of said amplifier; a third resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said first input terminal of said amplifier; a first capacitor having a first terminal coupled to said first input of said amplifier, and a second terminal coupled to said first output of said amplifier; second circuit means coupled to said amplifier for receiving said single-ended input signal, said second circuit means implementing a second part of said predetermined transfer function; a second capacitor coupled between said first circuit means and said second circuit means for implementing a third part of the predetermined transfer function, said second capacitor utilizing a voltage between said single-ended input signal and said reference voltage; and common mode sensing means coupled between said first and second output terminals, for sensing and providing to said amplifier a common mode voltage having a value between a signal voltage on said first output terminal of said amplifier and a signal voltage on said second output terminal of said amplifier.

Claim 3

The circuit of claim 1 wherein said second circuit means comprises: a fourth resistor having a first terminal for receiving the single-ended input signal, and a second terminal; a fifth resistor having a first terminal coupled to said second terminal of said fourth resistor, and a second terminal coupled to said second input terminal of said amplifier; a sixth resistor having a first terminal coupled to said second terminal of said fourth resistor, and a second terminal for receiving said reference voltage; and a third capacitor having a first terminal coupled to said second input terminal of said amplifier, and a second terminal coupled to said second output terminal of said amplifier.

Claim 4

The circuit of claim 2 wherein said first input terminal of said amplifier is a negative input terminal, and wherein said second input terminal is a positive input terminal of said amplifier.

Claim 5

The circuit of claim 3 wherein said first output terminal of said amplifier is a positive output terminal, and wherein said second output terminal is a negative output terminal of said amplifier.

Claim 6

A circuit comprising: amplification means for providing a differential voltage between positive and negative output signals proportional to a difference in voltage between a positive input terminal and a negative input terminal of said amplification means, and for changing a common mode voltage between said positive and negative output signals in response to a difference between a first reference voltage and a common mode feedback signal; common mode feedback means coupled to said amplification means, for providing said common mode feedback signal in response to a sensed common mode voltage between said positive output terminal and said negative output terminal; a first resistor having a first terminal coupled to a second reference voltage, and a second terminal; a second resistor having a first terminal for receiving a single-ended input signal, and a second terminal; a third resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said negative input terminal of said amplification means; a fourth resistor having a first terminal coupled to said second terminal of said second resistor, and a second terminal coupled to said positive input terminal of said amplification means; a first capacitor having a first electrode coupled to said second terminal of said first resistor, and a second electrode coupled to said second terminal of said second resistor; a fifth resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said positive output signal; a second capacitor having a first electrode coupled to said positive output signal, and a second electrode coupled to said negative input terminal of said amplifier; a sixth resistor having a first terminal coupled to said second terminal of said second resistor, and a second terminal coupled to said second reference voltage; and a third capacitor having a first electrode coupled to said positive input terminal of said amplifier, and a second electrode coupled to said negative output signal.

Claim 7

A circuit comprising: amplification means for providing a differential voltage between positive and negative output signals proportional to a difference in voltage between a positive input terminal and a negative input terminal of said amplification means, and for changing a common mode voltage between said positive and negative output signals in response to a difference between a first reference voltage and a common mode feedback signal; common mode feedback means coupled to said amplification means, for providing said common mode feedback signal in response to a sensed common mode voltage between said positive output terminal and said negative output terminal; a first resistor having a first terminal coupled to a second reference voltage, and a second terminal; a second resistor having a first terminal for receiving a single-ended input signal, and a second terminal; a third resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said negative input terminal of said amplification means; a fourth resistor having a first terminal coupled to said second terminal of said second resistor, and a second terminal coupled to said positive input terminal of said amplification means; a first capacitor having a first electrode coupled to said second terminal of said first resistor, and a second electrode coupled to said second terminal of said second resistor; a fifth resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said positive output signal; a second capacitor having a first electrode coupled to said positive output signal, and a second electrode coupled to said negative input terminal of said amplifier; a sixth resistor having a first terminal coupled to said second terminal of said second resistor, and a second terminal coupled to said second reference voltage; and a third capacitor having a first electrode coupled to said positive input terminal of said amplifier, and a second electrode coupled to said negative output signal.

Claim 8

The circuit of claim 5 wherein said first and second resistors have substantially equal resistances, said third and fourth resistors have substantially equal resistances, and said fifth and sixth resistors have substantially equal resistances.

Claim 9

The circuit of claim 5 wherein said second and third capacitors have substantially equal capacitances.

Claim 10

The circuit of claim 5 wherein said first and second reference voltages are substantially equal.

Claim 11

A circuit a comprising: an amplifier having positive and negative input terminals, and positive and negative output terminals; a first resistor having a first terminal for receiving a first voltage, and a second terminal; a second resistor having a first terminal for receiving a second voltage, and a second terminal; a third resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said negative input terminal of said amplifier; a fourth resistor having a first terminal coupled to said second terminal of said second resistor, and a second terminal coupled to said positive input terminal of said amplifier; a first capacitor having a first electrode coupled to said second terminal of said first resistor, and a second electrode coupled to said second terminal of said second resistor; a fifth resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said positive output terminal; a second capacitor having a first electrode coupled to said positive output terminal of said amplifier, and a second electrode coupled to said negative input terminal of said amplifier; a sixth resistor having a first terminal coupled to said second terminal of said second resistor, and a second terminal coupled to a reference voltage; a third capacitor having a first electrode coupled to said positive input terminal of said amplifier, and a second electrode coupled to said negative output terminal of said amplifier; and common mode means, coupled to said amplifier, for providing a common mode feedback signal to said amplifier.

Claim 12

A circuit a comprising: an amplifier having positive and negative input terminals, and positive and negative output terminals; a first resistor having a first terminal for receiving a first voltage, and a second terminal; a second resistor having a first terminal for receiving a second voltage, and a second terminal; a third resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said negative input terminal of said amplifier; a fourth resistor having a first terminal coupled to said second terminal of said second resistor, and a second terminal coupled to said positive input terminal of said amplifier; a first capacitor having a first electrode coupled to said second terminal of said first resistor, and a second electrode coupled to said second terminal of said second resistor; a fifth resistor having a first terminal coupled to said second terminal of said first resistor, and a second terminal coupled to said positive output terminal; a second capacitor having a first electrode coupled to said positive output terminal of said amplifier, and a second electrode coupled to said negative input terminal of said amplifier; a sixth resistor having a first terminal coupled to said second terminal of said second resistor, and a second terminal coupled to a reference voltage; a third capacitor having a first electrode coupled to said positive input terminal of said amplifier, and a second electrode coupled to said negative output terminal of said amplifier; and common mode means, coupled to said amplifier, for providing a common mode feedback signal to said amplifier.

Claim 13

The circuit of claim 9 wherein said common mode means is coupled between said positive and negative output terminals of said amplifier, and senses and provides to said amplifier said common mode feedback signal at a voltage having a value between a signal voltage on said positive output terminal of said amplifier and a signal voltage on said negative output terminal of said amplifier.

Claim 14

The circuit of claim 10 wherein said common mode means comprises: a seventh resistor having a first terminal coupled to said positive output terminal of said amplifier, and a second terminal providing said common mode feedback signal; and an eighth resistor having a first terminal coupled to said second terminal of said seventh resistor, and a second terminal coupled to said negative output terminal of said amplifier.