Source-coupled differential low-swing driver circuits
First Claim
1. An output driver for differential signal output, comprisinga cascoded current source attached to a first stable voltage source, having a current-source transistor driven by a first input bias voltage in series with a cascode transistor driven by a second input reference voltage,a pair of differential current-steering metal-oxide-semiconductor field-effect transistors with their drain terminals connecting together and to the cascoded current source, and source terminals providing differential output signals of the driver,wherein signal voltage transitions at gate and source terminals of each differential current-steering metal-oxide-semiconductor field-effect transistor are in phase.
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Abstract
A novel source-coupled differential driver circuit fully compatible with digital visual interface TMDS signaling specification is disclosed. Driven output signals are connected to the source terminals of driving switches in the invention circuit, minimizing the detrimental impact of miller coupling capacitance between gate nodes and driven output nodes upon output slew-rate, enabling higher frequencies of operation. Output signal undershoots and overshoots are also mitigated by the invention driver circuit due in part to the in-phase relationship of the gate node to the driven output node of a driver switch. Overall link performance is significantly enhanced by this SCDL driver architecture due to improved slew rates and signal integrity.
12 Citations
17 Claims
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1. An output driver for differential signal output, comprising
a cascoded current source attached to a first stable voltage source, having a current-source transistor driven by a first input bias voltage in series with a cascode transistor driven by a second input reference voltage, a pair of differential current-steering metal-oxide-semiconductor field-effect transistors with their drain terminals connecting together and to the cascoded current source, and source terminals providing differential output signals of the driver, wherein signal voltage transitions at gate and source terminals of each differential current-steering metal-oxide-semiconductor field-effect transistor are in phase.
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12. A method for output signal generation, comprising:
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steering a current developed in a current source through one or more MOS field-effect transistors, whose source terminals provide output signals, by providing activating electrical signals to said MOS field-effect transistors. wherein a miller coupling capacitance of the MOS field-effect transistor conveys a portion of its activating electrical signal energy to an output signal in phase with output voltage change, assisting output signal development. - View Dependent Claims (13, 14, 15, 17)
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Specification