Methods and Apparatus for Low Power Hard Disk Drive Servo Writers

A servo writer in a hard disk drive write system, comprising:

• a distribution circuit having:
• a first differential NPN transistor pair to coupled to a pulse generator via their bases, the first differential NPN transistor pair being coupled to a current sink via their emitters to sink a predetermined current to a reference signal via their emitters;
• a second differential NPN transistor pair, the emitters of the second differential NPN transistor pair being coupled to the collectors of the first differential NPN transistor pair via respective first and second resistors, the collectors of the second differential NPN transistor pair being coupled to the power source, and the bases of the of the second differential NPN transistor pair being coupled to a first switching circuit;
• and
• one or more signal generators coupled to the distribution circuit, the signal generators having one or more switches to selectively enable a first write mode or a second write mode, the switches having:
• a third differential NPN transistor pair, the emitters of the third differential NPN transistor pair being coupled to the respective collectors of the first differential NPN transistor pair, the collectors of the third differential NPN transistor pair being coupled to a power source via respective first and second resistors, and the bases of the of the third differential NPN transistor pair being coupled to a second switching circuit;
• and
• a fourth differential NPN transistor pair, the base of the fourth differential NPN transistor pair being coupled to the respective collectors of the first differential NPN transistor pair, the emitters being coupled to the reference signal via respective second and third current sinks, the collectors of the fourth differential NPN transistor pair being coupled to the power source.