Abstract: A read/write preamplifier configured for interconnection with a magnetic head through head contacts. The preamplifier includes a write control switching circuit electrically connected between first and second supply terminals and connected to the head contacts, for controlling current flow through the magnetic head. The switching circuit includes at least one transistor. A first PNP-type transistor is connected between the first supply terminal and the at least one transistor of the write control switching circuit, for controlling current flow to the write control switching circuit so as to cause the switching circuit to be driven between selected and unselected states. A PNP-type transistor bias circuit includes a mode-controlled current sink coupled between the first and second supply terminals and to the first PNP-type transistor.

Abstract: An open head detection circuit for detecting an open-circuit condition in a magnetic head connected to head contacts. The detector circuit includes a threshold source which generates a threshold voltage that is between a head contact voltage representative of a connected head and a head contact voltage representative of an open head. A comparator, coupled to receive head voltage signals from the head contacts and coupled to the threshold source, compares the head voltage signals to the threshold voltage and generates comparator signals representative of the comparison. Sampling circuitry, coupled to the comparator and coupled to receive write data signals, samples the comparator signals after detection of the write data signals and before the write data signals affect the comparator signals.