Patent ID: 7151393

Claim:
A write driver having first and second nodes for connection to a write head, the write driver comprising: first and second transistors each having a first terminal, a second terminal, and a base terminal, wherein said first terminals of said two transistors are respectively coupled to said first and second nodes; a common mode voltage control circuit coupled to said each transistor, said common mode voltage control circuit comprising a feedback circuit for each transistor between said first terminal and at least one of said base terminal and said second terminal to adjust a common mode voltage at said first terminals; wherein the common mode voltage control circuit further comprises: a first operational amplifier having a positive input connected to a common point between the first terminals, a negative input connected to the ground, and an output connected to the base terminals of the transistors; and a differential mode voltage control circuit coupled to said each transistor, said differential mode voltage control circuit comprising a feedback circuit for each transistor between said first terminal and said base terminal to adjust a differential mode voltage at said first terminals.