Patent ID: 6693489
Filing Date: 2004-02-17
Classification: H03F

Abstract:
A level shift circuit to voltage shift an input common-mode voltage of input complementary signals to an output common-mode voltage of output complementary signals, comprising:a differential pair of bipolar transistors having bases to respectively receive said input complementary signals, emitters coupled in common to a first current source, and collectors respectively coupled to first and second resistive elements; a pair of emitter-follower outpct bipolar transistors having bases respectively coupled to the collectors of said differential pair of bipolar transistors, emitters respectively coupled to second and third current sources, and collectors coupled to a power supply rail, wherein said output complementary signals are respectively produced at said emitters of said emitter-follower output bipolar transistors; and a voltage drop device connected between said power supply rail and said first and second resistive elements, wherein said voltage drop device causes a voltage drop related to said voltage shift; wherein said first current source comprises an open-collector-output operational amplifier, wherein a tail current of said first current source varies inversely with a difference between a reference voltage applied to a positive terminal of said operational amplifier and a feedback voltage applied to a negative terminal of said operational amplifier, wherein said feedback voltage is related to said output common-mode voltage.