Differential data driver
AssigneeNortel Networks Limited
InventorAnthony Kevin Dale Brown
Life of this patent
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Abstract
A digital data driver includes a differential amplifier having transistors which operate as a push-pull amplifier in class C mode. The transistors are conductive or non-conductive and controlled in response to a differential data input signal. The driver provides current to a load resistor of an external equipment and the direction of the current flowing therein is reversed in response to the input data. The differential amplifier transistors are connected to other transistors which provide source impedance to the external equipment. The source impedance of the driver is a controllable characteristic impedance of e.g., 50 .OMEGA..
Claims16
A differential data driver for providing a differential data output signal to external equipment including a resistive load element, in response to a differential data input signal, the driver comprising:
- differential inputs for receiving the input signal;
- differential outputs for connection to the load element of the external equipment;
- differential means for providing the output signal to the load element via the outputs, the differential means including first and second amplifier means and first current means, each of the first and second amplifier means operating in class C mode, each of the first and second amplifier means including a first transistor and impedance means, the collector of the first transistor being connected to the respective output and impedance means, each of the impedance means comprising a resistive circuit, each of the resistive circuits comprising a second transistor and a first resistive element connected to the emitter of the respective second transistor, the emitters of the first transistors of the first and second amplifier means being coupled and connected to the first current means;
- driving means for enabling the differential means to provide the output signal to the load element in response to the input signal received by the differential inputs, so that the polarity of the output signal is controlled and current flows in the load element with respect to the polarity, the driving means comprising first and second response means for providing first and second drive signals of opposite polarities in response to the input signal, the driving means further comprising first and second push-pull drive means for driving the first and second amplifier means, each of the amplifier means being operative in a push or pull mode, in response to the respective drive signal, so that the differential means operates as a push-pull amplifier, each of the push-pull drive means comprising a third transistor and a second resistive element connected to the collector of the respective third transistor, the junction of each of the second resistive elements and the collector of the respective third transistor being connected to the base of the respective second transistor;
- and
- first and second feedback means for providing negative feedback signals from the differential means to the respective push-pull drive means.
Dependencies are inferred from the claim text.