Miscellaneous active electrical nonlinear devices – circuits – and – Gating – Converging with plural inputs and single output
Reexamination Certificate
2002-11-08
2004-04-13
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Gating
Converging with plural inputs and single output
Reexamination Certificate
active
06720818
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates in general to electronic circuits and more specifically to differential multiplexers.
Multiplexers allow selection of a signal from a number of signals. In response to a control signal, a multiplexer input receiving the selected signal is connected to the output of the multiplexer. Multiplexers are used in a variety of circuits and environments and are often used in differential signal circuits such as Current Mode Logic (CML) circuits. In a two input multiplexer for example, a differential signal pair is received at a first differential input and another differential signal pair is received at a second differential input. In response to a select signal and its compliment, the signal received at one of the differential signal inputs is directed to a differential output of the multiplexer. Due to their architecture, however, conventional differential multiplexers are limited in that the amplitude or “output swing” of the output signal is often less than a maximum value. Conventional techniques used to increase the amplitude of the output signals result in an increased current draw and power consumption. Therefore, there is a need for a differential multiplexer that efficiently provides an output signal with a maximum amplitude.
SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, the amplitude of a differential output signal at a differential multiplexer is efficiently maximized by presenting, in response to a differential selection signal, a high impedance to each output port of each differential transistor of a non-selected differential transistor pair. The exemplary differential multiplexer includes a selection transistor connected to the output port of each transistor of a differential transistor pair that receives a differential input signal. In response to the differential selection signal, each of the selection transistors connected to the non-selected differential transistor pair is placed in an off state resulting in a high impedance between the output ports of the transistors of the non-selected differential transistor pair.
REFERENCES:
patent: 5289048 (1994-02-01), Ishihara et al.
patent: 5801571 (1998-09-01), Allen et al.
patent: 6385214 (2002-05-01), Kikuchi et al.
Bryan Thomas Clark
Dang Harry Huy
Lei Shuyu
Liu Zhixiang Jason
Applied Micro Circuits Corporation
Cunningham Terry D.
INCAPLAW
Meador Terrance A.
Tru Quan
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