System and method for providing a constant swing high-gain complementary differential limiting amplifier
AssigneeNational Semiconductor Corporation
InventorsRamsin M. Ziazadeh, Yongseon Koh
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Abstract
A system and a method are disclosed for providing a constant swing high-gain complementary differential limiting amplifier. High gain for the differential amplifier is created by providing a current to the driving transistors that is a combination of any of (a) constant current, (b) transconductance based current, and (c) temperature compensated based current. A constant differential output swing is created by providing a varying differential current to the output load resistors of the differential amplifier that tracks process and temperature variations within the output load resistors.
Claims21
A differential amplifier circuit of a type comprising a first driving transistor, a second driving transistor, a first output load resistor, and a second output load resistor, said differential amplifier circuit comprising:
- means for providing a varying differential current through said first and second output load resistors that tracks process and temperature variations within said first and second output load resistors;
- and
- means for providing a differential current through said first and second driving transistors.
A differential amplifier circuit of a type comprising a first NMOS driving transistor, a second NMOS driving transistor, a first output load resistor, and a second output load resistor, said differential amplifier circuit comprising:
- a first current source having a first end coupled to sources of said first and second NMOS driving transistors and a second end coupled to ground;
- and
- a differential pair of transistors comprising a third transistor and a fourth transistor, wherein a gate of the first NMOS driving transistor is coupled to a negative input signal, a gate of the second NMOS driving transistor is coupled to a positive input signal, a gate of the third transistor is coupled to the negative input signal, a gate of the fourth transistor is coupled to the positive input signal, a drain of the third transistor is coupled to a drain of the second NMOS driving transistor, and a drain of the fourth transistor is coupled to a drain of the first NMOS driving transistor.
A method for providing a differential amplifier circuit that has a constant differential output swing and high gain, said method comprising the steps of:
- providing a differential amplifier circuit that comprises a first driving NMOS transistor, a second driving NMOS transistor, a first output load resistor, and a second output load resistor;
- coupling a first current source to sources of the first and second driving NMOS transistors;
- and
- coupling a differential pair of transistors comprising a third transistor and a fourth transistor to the first and second driving NMOS transistors;
- wherein a gate of the first driving NMOS transistor is coupled to a negative input signal, a gate of the second driving NMOS transistor is coupled to a positive input signal, a gate of the third transistor is coupled to the negative input signal, a gate of the fourth transistor is coupled to the positive input signal, a drain of the third transistor is coupled to a drain of the second driving NMOS transistor, and a drain of the fourth transistor is coupled to a drain of the first driving NMOS transistor.
Dependencies are inferred from the claim text.