Voltage signal line driver comprising a push-pull bridge amplifier
AssigneeLucent Technologies Inc.
InventorKadaba R. Lakshmikumar
Life of this patent
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Abstract
A line driver having two halves arranged in a push-pull configuration. Each half has a pass transistor, connected between a power supply rail and an output terminal, and an amplifier with an output coupled to the output terminal. Only one of the pass transistors conducts at any given time. A sense transistor, coupled between the power supply rail and the input of the amplifier, varies the output of the amplifier to compensate for variations in the conductivity of the conducting pass transistor. Preferably, the current density in the sense transistor is substantially the same as in the conducting pass transistor.
Claims14
In an integrated circuit, a balanced line driver has two portions, wherein the two portions are coupled to a load therebetween, each portion having:
- a switching transistor, coupled between a power supply rail and an output terminal;
- and
- an amplifier responsive to an input signal applied to an input and having an output coupled to the output terminal;
- wherein the balanced line driver is CHARACTERIZED BY:
- a sense transistor, connected between the power supply rail and the input of the amplifiers, for compensating for variations in the conductivity of the switching transistors caused by variations in transistor characteristics.
A method of compensating for conduction variations of a conducting switching transistor in a balanced line driver having two portions, each portion having:
- a switching transistor, coupled between a power supply rail and an output terminal;
- and
- an amplifier having an input and an output, the output coupled to the output terminal;
- wherein only one of the switching transistors is conducting at any one time, the other transistor being substantially non-conducting at that time;
- CHARACTERIZED BY THE STEPS OF:
- amplifying by one of the amplifiers an input signal applied to the input thereof;
- generating a compensating signal from a sense transistor;
- applying the compensating signal to the amplifier amplifying the input signal;
- wherein the compensating signal is amplified by the amplifier to compensate for the variations in the conductivity of the conducting switching transistor caused by variations in transistor characteristics.
Dependencies are inferred from the claim text.