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US 4,383,223 AGranted
CMOS Operational amplifier employing push-pull output stage
AssigneeMotorola, Inc.
InventorRichard W. Ulmer
Life of this patent
Estimating the term…
Abstract
A CMOS operational amplifier includes a biasing scheme for supplying current to a differential stage. A push-pull output stage includes a current sinking transistor which is coupled to a first output of the differential stage. A current mirror is coupled between a second output of the differential stage and the gate electrode of a current sourcing device in the output stage.
Claims8
A CMOS operational amplifier, comprising:
- a differential stage having first and second inputs and first and second outputs, said first and second inputs for receiving first and second input voltages;
- a first field-effect transistor having its current conducting path coupled between said second output and ground, and the gate electrode thereof coupled to said second output;
- a second field-effect transistor having its current conducting path coupled between said first output and ground, and the gate electrode thereof coupled to the gate electrode of said first field-effect transistor;
- first means coupled to said differential state and to a supply voltage terminal for supplying a constant current to said differential stage;
- a push-pull output stage coupled to said supply voltage terminal and having third and fourth inputs, said third input coupled to said first output;
- and
- third and fourth field-effect transistors, said third field-effect transistor having a first current electrode coupled to said supply voltage terminal and both a second current electrode and a gate electrode connected together and coupled to said fourth input, and said fourth field-effect transistor having a first current electrode coupled to the second current electrode of said third field-effect transistor, a second current electrode connected directly to ground, and a gate electrode coupled to said second output.
4 more elements
An operational amplifier, comprising:
- a differential stage having first and second inputs and first and second outputs, said first and second inputs for receiving first and second input voltages;
- a first field-effect transistor having its current conducting path coupled between said second output and ground, and the gate electrode thereof coupled to said second output;
- a second field-effect transistor having its current conducting path coupled between said first output and ground, and the gate electrode thereof coupled to the gate electrode of said first field-effect transistor;
- first means coupled to said differential stage and to a supply voltage terminal for supplying a constant current to said differential stage;
- third and fourth field-effect transistors having their current conducting paths coupled in series between said supply voltage terminal and ground, said third field-effect transistor being diode connected and said fourth field-effect transistor having a gate electrode coupled to said second output;
- a push-pull output stage comprising fifth and sixth field-effect transistors, said fifth field-effect transistor having a first current electrode coupled to said supply voltage terminal, a gate electrode coupled to a gate electrode of said third field-effect transistor, and a second current electrode, said sixth field-effect transistor having a first current electrode coupled to the second current electrode of said fifth field-effect transistor, a gate electrode coupled to said first output, and a second current electrode coupled to ground.
3 more elements
An operational amplifier, comprising:
- a differential stage having first and second inputs and first and second outputs, said first and second inputs for receiving first and second input voltages;
- a first field-effect transistor having its current conducting path coupled between said second output and ground, and the gate electrode thereof coupled to said second output;
- a second field-effect transistor having its current conducting path coupled between said first output and ground, and the gate electrode thereof coupled to the gate electrode of said first field-effect transistor;
- current source means coupled to said differential stage and to a supply voltage terminal for supplying a constant current to said differential stage;
- third and fourth field-effect transistors comprising a push-pull output stage having their current conducting paths coupled in series between said supply voltage terminal and ground, a gate electrode of said third field-effect transistor forming a first input of said push-pull output stage and a gate electrode of said fourth field-effect transistor forming a second input of said push-pull output stage which is coupled to the first output of said differential stage;
- and
- fifth and sixth field-effect transistors having their current conducting paths coupled in series between said supply voltage terminal and ground, said fifth field-effect transistor being diode connected and having a gate electrode coupled to the gate electrode of said third field-effect transistor, and said sixth field-effect transistor having a gate electrode coupled to the second output of said differential stage.
4 more elements
Dependencies are inferred from the claim text.