Single supply amplifier with swing to ground

A method performed by an amplifier circuit comprising:

• receiving an input voltage Vin at a voltage input terminal;
• outputting an output voltage Vout at a voltage output terminal, the output terminal being coupled to a pull up circuit and a pull down circuit;
• receiving Vin and a first feedback voltage corresponding to Vout by a differential input stage, the differential input stage generating a first signal;
• controllably pulling down the voltage output terminal to control Vout by the method comprising:
• controlling a first transistor by the first signal to pull down the voltage output terminal to generate the first feedback voltage to substantially match Vin when Vout is above a transition voltage Vtrans;
• and
• controlling a second transistor, connected in parallel with the first transistor, by the first signal to pull down the voltage output terminal to generate the first feedback voltage to substantially match Vin when Vout is below Vtrans,
• wherein a majority of current from the Vout terminal is conducted by the first transistor when Vout is above Vtrans, and a majority of the current from the Vout terminal is conducted by the second transistor when Vout is below Vtrans, and
• wherein the second transistor operates in its active region during a time when Vout falls below Vtrans, while the first transistor operates outside of its active region during a time when Vout falls below Vtrans.

A method performed by an amplifier circuit comprising:

• receiving an input voltage Vin at a voltage input terminal;
• outputting an output voltage Vout at a voltage output terminal, the output terminal being coupled to a pull up circuit and a pull down circuit;
• receiving Vin and a first feedback voltage corresponding to Vout by a differential amplifier, the differential amplifier generating a first signal;
• controllably pulling up the voltage output terminal to control Vout by the method comprising:
• controlling a first transistor by the first signal to pull up the voltage output terminal to generate the first feedback voltage to substantially match Vin when Vout is below a transition voltage Vtrans;
• and
• controlling a second transistor, connected in parallel with the first transistor, by the first signal to pull up the voltage output terminal to generate the first feedback voltage to substantially match Vin when Vout is above Vtrans,
• wherein a majority of current from the Vout terminal is conducted by the first transistor when Vout is below Vtrans, and a majority of the current from the Vout terminal is conducted by the second transistor when Vout is above Vtrans, and
• wherein the second transistor operates in its active region during a time when Vout rises above Vtrans, while the first transistor operates outside of its active region during a time when Vout rises above Vtrans.