Adjustable Write Current Source
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
The DAC Adjustable Write Current Source provides the capability to randomly select eight different values of write current, such that the optimal value of write current is attained for a particular head/disk combination, at a particular radial location. Moreover, the selected write current is within 5% of the specified value. This tolerance value is achieved without the use of costly active laser trimming. The DAC Adjustable Write Current Source provides an accurate write current value by making use of a precision reference that is generated on the electronics card. The reference voltage is applied to the negative inputs of the two operational amplifier of the DAC Adjustable Write Current Source as shown in the figure. Operational amplifier Op2 forms a current source with transistor Q9 and external resistor R21.