Miscellaneous active electrical nonlinear devices – circuits – and – Gating – Converging with plural inputs and single output
Reexamination Certificate
1998-12-08
2001-10-30
Tran, Toan (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Gating
Converging with plural inputs and single output
C327S099000
Reexamination Certificate
active
06310509
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to signal routing, and in particular to a differential multiplexer with high bandwidth and reduced crosstalk.
BACKGROUND OF THE INVENTION
In signal routing, multiplexing two or more signals is frequently desirable. In a typical multiplexer, two or more input signals and a select signal are received. The input signal indicated by the select signal is then buffered through to the output of the multiplexer.
In a multiplexer, it is desirable to reduce or eliminate the amount of crosstalk between input channels. It is also desirable, in high-speed signal routing applications, to maximize the output slew rate of the multiplexer in order to enable the multiplexer to maintain signal fidelity at the highest data rates.
SUMMARY OF THE INVENTION
Therefore, a need has arisen for a multiplexer that addresses the disadvantages and deficiencies of the prior art. In particular, a need has arisen for a multiplexer with high bandwidth and reduced crosstalk.
Accordingly, an improved multiplexer is disclosed. In one embodiment, the multiplexer includes a first input device that receives a first input signal and a first select signal. When the first select signal has a first state, the first input device generates a first voltage at a first node in response to the first input signal. When the first select signal has a second state, the first input device generates a first reference voltage at the first node. A second input device receives a second input signal and a second select signal related to the first select signal. When the second select signal has a first state, the second input device generates a second voltage at a second node in response to the second input signal. When the second select signal has a second state, the second input device generates a second reference voltage at the second node. A first output buffer has an input terminal coupled to the first node and an output terminal coupled to an output node. The first output buffer tracks the first voltage at the output terminal, and presents a high impedance at the output terminal when the first reference voltage is present at the first node. A second output buffer has an input terminal coupled to the second node and an output terminal coupled to the output node. The second output buffer tracks the second voltage at the output terminal, and presents a high impedance at the output terminal when the second reference voltage is present at the second node.
An advantage of the present invention is that the multiplexer inputs are isolated, reducing or eliminating crosstalk between input channels. Another advantage of the present invention is that internal slew rates are increased, thereby increasing the output slew rate of the multiplexer and maximizing the bandwidth capability of the multiplexer.
REFERENCES:
patent: 5045804 (1991-09-01), Sugawara et al.
patent: 6137340 (2000-10-01), Goodell et al.
patent: 6211722 (2001-04-01), Mattia et al.
patent: 6239646 (2001-05-01), Navabi et al.
Davenport William H.
Turudic Andy
Allenby Christopher B.
Skjerven Morrill & MacPherson LLP
Tran Toan
Triquint Semiconductor, Inc.
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