Abstract: An apparatus for characterizing impedance presented to a write driver device in a write head assembly for use with an electromagnetic storage product includes: (a) a test impedance unit coupled with the write driver device; and (b) a measuring unit coupled with the test impedance unit. The measuring unit receives a measured parameter associated with the test impedance unit and compares the measured parameter with a reference parameter. The measuring unit indicates a result of the comparing.

Abstract: An apparatus for monitoring changes in a magnetic field using a magneto-resistive device situated in the field includes a first and second input locus coupled with the magneto-resistive device. An amplifier means for amplifying electrical signals has input terminals and output terminals. A first input terminal is coupled with the first input locus with a first capacitor coupled in series between the first input locus and the first input terminal. A second input terminal is coupled with the second input locus with a second capacitor coupled in series between the second input locus and the second input terminal. The apparatus receives a bias current at the first input locus that cooperates with the magneto-resistive element to affect electrical potential at the first input locus. The amplifier device presents at least one output signal at the output terminals indicating changes in the magnetic field.

Abstract: A circuit (50) and method are provided for generating a signal (84) indicating an open impedance fault of a coil (56) of a write head (18) of a mass data storage device (10). The circuit (10) includes a differential amplifier (51) with the electrical component (56) being connected as a load in a first leg thereof. An impedance element (64) is provided in a second leg of the differential amplifier (50), and a pair of bipolar transistors (52,54) are respectively connected in the first and second legs. The pair of bipolar transistors (52,54) have a constant bias voltage (Bias) applied to inputs thereof, and an output circuit is connected to an output node of the first leg of the differential amplifier (51).

Abstract: A circuit (50) and method are provided for generating a signal (84) indicating an open impedance fault of a coil (56) of a write head (18) of a mass data storage device (10). The circuit (10) includes a differential amplifier (51) with the electrical component (56) being connected as a load in a first leg thereof. An impedance element (64) is provided in a second leg of the differential amplifier (50), and a pair of bipolar transistors (52,54) are respectively connected in the first and second legs. The pair of bipolar transistors (52,54) have a constant bias voltage (Bias) applied to inputs thereof, and an output circuit is connected to an output node of the first leg of the differential amplifier (51).

Abstract: The present invention provides an apparatus, system and method of improving the bias response time for pre-amplifier circuits which utilize noise reduction capacitors 275. The system uses a quick recovery circuit 210 electrically connected to the capacitive node 216 of the pre-amplifier circuit. The quick recovery circuit 210 comprises a gain amplifier 218 with a resistive input and a controlled current source 219. The controlled current source corresponds to adjustments in a controlled current source 225 of the pre-amplifier and is electrically connected to the resistive input of the gain amplifier 218. The gain amplifier 218 can be selectively switched 211 to operatively connect an output to the capacitive node 216 of the pre-amplifier circuit.

Abstract: The present invention provides an apparatus, system and method of improving the bias response time for pre-amplifier circuits which utilize noise reduction capacitors 275. The system uses a quick recovery circuit 210 electrically connected to the capacitive node 216 of the pre-amplifier circuit. The quick recovery circuit 210 comprises a gain amplifier 218 with a resistive input and a controlled current source 219. The controlled current source corresponds to adjustments in a controlled current source 225 of the preamplifier and is electrically connected to the resistive input of the gain amplifier 218. The gain amplifier 218 can be selectively switched 211 to operatively connect an output to the capacitive node 216 of the pre-amplifier circuit.

Abstract: A single ended differential input amplifier is used as the initial amplification stage of a preamplifier used in the read channel of a hard disk drive (HDD) application. Over the usable bandwidth of the read channel (typically between about 1 to 100 megahertz), prior art single ended differential input amplifiers are susceptible to noise coupling from the power supply. The invention enhances the power supply noise rejection (PSR) ability of single ended differential input amplifiers by adding a resistor in series with the capacitor that is usually coupled across one leg of the differential amplifier. As the frequencies across the usable bandwidth increase and the capacitor tends to short, the added resistor is effective to maintain impedance without affecting the gain of the amplifier.

Abstract: A circuit for the Class-A differential amplification of two input signals.A first constant current source 22 is connected between a voltage supply terminal 3 and a node 8. A second constant current source 24 is connected between the supply terminal 3 and a node 9. A first transistor T1, with a control electrode connected to input terminal 1, has a conduction path connected between node 8 and a voltage supply terminal 10. A second transistor T2, with a control electrode connected to input terminal 2, has a conduction path connected between node 9 and terminal 10. A third transistor T3, with a control electrode connected to input terminal 1, has a conduction path connected between node 9 and an output terminal 6. Finally, a fourth transistor T4, with a control electrode connected to input terminal 2, has a conduction path connected between node 8 and an output terminal 7.