US 2010/0301905 A1 · Output circuit having pre-emphasis function

Abstract

An output circuit includes a first differential pair of transistors driven by a first current source and differentially receiving input signals and a second differential pair of transistors driven by a second current source and differentially receiving first control signals (EMT, EMB). Output pairs of the first and second differential pairs are connected to the differential output terminals. A load resistor element pair is connected between a power supply and the differential output terminals. The output circuit further includes a third differential pair of transistors driven by a third current source and differentially receiving second control signals and a fourth differential pair of transistors driven by a fourth current source and differentially receiving third control signals. An output pair of the third differential pair of transistors is connected between one of the differential output terminals and the power supply. An output pair of the fourth differential pair of transistors is connected between the power supply and the other of the differential output terminals.

Claims12

Dependent claims

An output circuit comprising:

first and second input terminals;
first and second output terminals;
a main buffer that receives differential input signals from the first and second input terminals and outputs differential output signals to the first and second output terminals;
a pre-emphasis buffer that applies pre-emphasis to the differential output signals at a time of a transition of the differential input signals;
and
a de-emphasis-level control buffer including
a differential circuit that turns on a path between one of the first and second output terminals and one of first and second power supplies to reinforce the pre-emphasis operation on the differential output signals at a time of the pre-emphasis by the pre-emphasis buffer, and that, at a time of de-emphasis, turns off the path through which the pre-emphasis has been reinforced and turns on another path between the first and second power supplies.

4 more elements

An output circuit comprising:

first and second input terminals;
first and second output terminals;
a first current source connected to a second power supply;
a first differential transistor pair driven by the first current source, the first differential transistor pair having an input pair connected to the first and second input terminals and having an output pair connected to the first and second output terminals;
a load resistor element pair connected between the first and second output terminals and a first power supply;
a second current source connected to the second power supply;
a second differential transistor pair driven by the second current source, the second differential transistor pair differentially receiving first control signals, the second differential transistor pair having an output pair connected to the first and second output terminals;
a third current source connected to the second power supply;
a third differential transistor pair driven by the third current source, the third differential transistor pair differentially receiving second control signals, the third differential transistor pair having an output pair connected to the second output terminal and the first power supply;
a fourth current source connected to the second power supply;
and
a fourth differential transistor pair driven by the fourth current source, the fourth differential transistor pair differentially receiving third control signals, the fourth differential transistor pair having an output pair connected to the first power supply and the first output terminal.

9 more elements

Dependencies are inferred from the claim text.

Output circuit having pre-emphasis function

Life of this patent

Output circuit having pre-emphasis function

Life of this patent

Abstract

Claims12