Abstract: A circuit and method for lowering the corner frequency of a differential preamplifier having an AC coupling circuit includes a compensation circuit to adjust the frequency response characteristics created by the AC coupling circuit. An RC network in the compensation circuit is configured to provide a canceling zero at the corner frequency of the AC coupling circuit. The RC network also provides a pole at a desired frequency lower than the corner frequency of the AC coupling circuit, in order to define the overall preamplifier corner frequency. The compensation circuit allows the capacitance in the AC coupling circuit to be significantly reduced, eliminating the need for external components or a very large integrated capacitance.

Abstract: A high-gain, high-bandwidth, low-noise differential common-emitter-common-base cascode preamplifier for use in the read circuitry of an MR head system includes a by-pass circuitry. Currents generated in load devices connected to the preamplifier are added to currents generated in the by-pass circuitry to provide the currents that flow through the common-emitter transistors of the preamplifier.

Abstract: A voltage controlled oscillator circuit is shown in integrated circuit chip design form. The frequency range of the circuit is extended by providing switch means for isolating the off-chip frequency determining capacitor and employing a minimum-value on-chip capacitor to control circuit maximum frequency operation. The circuit is based upon a regenerative latch operation which switches a controlled current to charge a capacitor first in one polarity and then in the other polarity. A control voltage determines the charging current and hence the frequency of operation.