Abstract: An integrated circuit module is designed with bypass switches in critical places to route signals around specific circuit blocks, e.g. an automatic gain control (AGC) system and an anti-aliasing filter. If there had been significant problems with either block, it can be bypassed and tests of the remaining circuits are possible. This allows all circuits in the module to be tested in the initial pass, reducing the risk of needing a third pass after the known problems were fixed in the second pass. Additionally, the bypass circuits are useful at module production test and for diagnostics in the final product.

Abstract: A write head circuit is provided having improved transient and steady state response. The circuit includes a dynamically coupled damping circuit that is coupled to the write head during transient periods of a write signal to substantially reduce or eliminate overshoot generated by a write head cable. During steady state or data writing periods, the damping circuit is decoupled from the write head to prevent unnecessary loading of the write head. In preferred embodiments, the damping circuit includes a resistor in series with a capacitor, and the damping circuit is coupled in parallel to the write head. The resistor substantially reduces the overshoot of a write signal supplied to the write head, while the capacitor decouples the resistor from the write head during steady state or data write periods.

Abstract: A reference current and resistance is used to determine a reference voltage. A variable current is then applied to the MR read head, and is adjusted to produce a voltage equal to that of the reference voltage. Then, the known current and voltage is used to determine the resistance of the MR read head.