Low voltage differential signal (LVDS) input circuit
AssigneeTelefonaktiebolaget LM Ericsson
InventorsJoakim Bängs, John Thompson, Raymond Filippi
Life of this patent
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Abstract
Problems associated with using bipolar differential circuits over a wide common mode voltage range are solved using first and second amplifier circuits 3 and 5, respectively operating over first and second voltage sub-ranges. The low voltage differential signal (LVDS) 1 is applied across a pair of series connected resistors 7 and 9, and to the inputs of the amplifiers 3 and 5. The common mode voltage signal 11 is fed to the inputs of third and fourth amplifiers 15 and 17. The third and fourth amplifiers 15 and 17 ensure that the LVDS receiver has a constant linear transfer characteristic over the differential input signal range and over the full common mode range, especially over the amplifier transition region.
Claims21
A circuit for receiving a low voltage differential input signal having a common mode voltage range, the circuit comprising:
- a first amplifier circuit which operates in a first voltage sub-range of the common mode voltage range;
- a second amplifier circuit which operates in a second voltage sub-range of the common mode voltage range;
- and
- a control circuit for controlling the operation of the first and second amplifier circuits so as to provide an output signal over the common mode voltage range of the input signal, and for controlling the summation of the outputs of the first and second amplifiers in an overlapping region of the first and second voltage sub-ranges.
A method of receiving a low voltage differential input signal having a common mode voltage range, the method comprising the steps of:
- providing a first amplifier circuit for operating in a first voltage sub-range of the common mode voltage range;
- providing a second amplifier circuit for operating in a second voltage sub-range of the common mode voltage range;
- and
- controlling the operation of the first and second amplifier circuits so as to provide an output signal over the common mode voltage range of the input signal, wherein the output signals from the first and second amplifiers are summed in an overlapping region of the first and second voltage sub-ranges.
Dependencies are inferred from the claim text.