Abstract: A first device comprising a first current mirror is used to amplify the output of a first photodetector. A second device comprising a current mirror arrangement is employed to amplify the output of a second photodetector. The outputs of the two devices are then compared to provide a signal useful for many applications, including that for determining the position of a rotating member or of a member in relative motion to another member. Preferably, no feedback action is used for the amplification of the output of at least one of the photodetectors.

Abstract: A first device comprising a first current mirror is used to amplify the output of a first photodetector. A second device comprising a current mirror arrangement is employed to amplify the output of a second photodetector. The outputs of the two devices are then compared to provide a signal useful for many applications, including that for determining the position of a rotating member or of a member in relative motion to another member. Preferably, no feedback action is used for the amplification of the output of at least one of the photodetectors.

Abstract: The DC level of the output of an amplifier may be dynamically adjusted depending on the operating conditions of the amplifier by comparing the output of the amplifier to a set reference value using a comparator. The output of the comparator is then fed to a state machine which adjusts the DC level of the amplifier output in an autocalibration process until the DC level of the output of the amplifier is substantially equal to the reference value. An undervoltage lockout circuit detects a power supply to the amplifier and causes the calibration to be initiated only when the power supply meets certain requirements. A change in the gain setting in the amplifier is also detected for automatically initiating the calibration process.

Abstract: A serializer/deserializer encoder-decoder for a disk drive achieves increased storage capacity through the use of partial response maximum likelihood class IV (PRML-IV) coding. Reduction of hardware requirements is realized by the integration of similar read and write mode functions into common circuit elements in order to reduce duplication. To this end, a data word selector selectively receives or sends data words in the write/read mode, respectively, from a data sequencer. Dependent upon the mode the data words are either provided to an encoder or received from a decoder for translation to/from code words. The encoder-decoder sends or receives the code words to a code word selector which in turn connects with the serializer-deserializer for coupling with the write or read channel.