Patent ID: 7696786

Claim:
A circuit for shifting the reference level of a differential signal while preserving its amplitude, the circuit comprising: a negative input terminal; a positive input terminal; a first load resistor having a first end and a second end, the first end connected to the negative input terminal; a second load resistor having a first end and a second end, the first end connected to the positive input terminal; a first pass transistor having a first node, a second node and a control node, the first node connected to the second end of the first load resistor to form a negative output terminal, the control node connected to a selected reference voltage signal; a current mirror having a first current node, a second current node and a current control node, the first current node connected to the second node of the first pass transistor, the second current node connected to the second end of the second load resistor to form a positive output terminal; and a first amplifier having a negative input, a positive input and an output, the positive input connected to the negative output terminal, the negative input connected to the selected reference voltage signal, the output connected to the current control node of the current mirror.