Front end stage of an operational amplifier
AssigneeHarris Corporation
InventorGerald M. Cotreau
Life of this patent
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Abstract
The front end of an operational amplifier having an improved slew rate and high gain current output capabilities. The amplifier includes a slew enhancement or large signal stage connected in parallel to a normal front end or small signal stage. The small signal stage supplies a transconductance output which is approximately linearly related to the input until its slew rate limit. The slew enhancement stage is designed to provide slew current when the small signal stage reaches a selected threshold such as its slew rate limit, thereby providing an increased output current response to an increasing differential input voltage beyond the slew rate of the small signal stage. The large signal stage can be optimized to provide a greater input linear dynamic range, faster slew rate and improved efficiency.
Claims16
In an amplifier circuit having an input and output stage, said circuit comprising:
- a small signal stage arranged in said input stage and having a transconductance for providing an output current in response to a small signal differential input voltage;
- a large signal stage arranged in said input stage and connected electrically in parallel with said small signal stage for providing additional current when said differential input voltage reaches a selected threshold, said large signal stage having a transconductance which is substantially the same in magnitude as the transconductance of said small signal stage;
- and
- summing means coupled between the outputs of said small signal stage and said large signal stage for providing a combined output current to said output stage of said amplifier circuit.
In an amplifier circuit having an input and an output stage, said circuit comprising:
- a small signal transconductance stage in said input stage for providing an output current in response to a differential input voltage, said response producing a first slew rate;
- a large signal transconductance stage connected electrically in parallel with said small signal transconductance stage for providing current only in response to said input differential voltage when said differential voltage reaches a selected threshold, said response producing a second slew rate, said second slew rate being faster than said first slew rate, and
- summing means coupled between the outputs of said small signal transconductance stage and said large signal transconductance stage for providing a combined output current to said output stage.
In an amplifier circuit having an input and an output stage, said circuit comprising:
- a small signal stage in said input stage for providing an output current in response to a small signal differential input voltage, said small signal stage including a first internal biasing current source means having a first fixed magnitude;
- a power efficient large signal stage connected electrically in parallel with said small signal stage for providing additional slew current only when said differential input voltage to said parallel stages reaches a specified value, said large signal stage including a second internal biasing current source means having a second fixed magnitude, wherein said additional slew current is greater in magnitude than the current available from said second internal biasing current source means;
- and
- summing means coupled between the outputs of said small signal stage and said large signal stage for providing a combined output current to said output stage.
Dependencies are inferred from the claim text.