Device and method for calibrating a time constant of one or more filter

Abstract

A control circuit for providing a stable, adjustable, time constant for use as a master time constant is presented. Used as a master time-constant circuit, this control circuit can ensure multiple slave circuits are precisely calibrated. The circuit includes a charging section that receives a series of calibrating pulses. The reference cell's voltage is compared to a reference voltage equal of Vcc/e. If the cell's voltage is below the reference voltage, a current source charges a capacitor, lowering the resistance of the transistor in the cell to correct the time circuit inaccuracy. Conversely, if the cell's voltage is above the reference voltage, a current sink discharges the capacitor, raising the transistor's resistance. This also corrects the time circuit inaccuracy. Thus, this circuit includes a method to correct time-constants which are too large or too small. This circuit is used in various applications where extreme accuracy and precision is needed, such as media drive read/write heads.