Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Nonlinear amplifying circuit
Patent
1997-01-03
1998-09-08
Tran, Toan
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Nonlinear amplifying circuit
327362, 327 65, 327350, G06G 712, H03G 1108
Patent
active
058050116
ABSTRACT:
Temperature and technology-independent self-calibrating monolithic logarithmic amplifier systems that use integrated cascades of current-summing or voltage-summing differential-limiter gain stages are disclosed. Each stage is trimmed and stabilized by a respective bias replicator cell and a current mirror cell. The bias replicator provides a bias current control signal in response to a change in a given difference between bias currents in a differential pair of amplifiers controlled by a predetermined differential calibration voltage. The differential pair is identical to a differential pair in the limiter amplifier. The differential calibration voltage E.sub.lin is well-within the linear portion of the amplifier's transfer curve during operation, so that the proportional relation between E.sub.k and E.sub.lin, which is the same as that between the given difference between currents and the correct bias current value I.sub.B, remains constant throughout. The bias replicator signal then varies the input bias current of the limiter amplifier to correct for temperature-related and technology-related bias-current errors. The current mirror uses an op amp connected to a calibration voltage equal to the correct limit voltage of the amplifier to detect a change from that voltage across a variable calibration resistance. The current mirror provides a signal to that variable calibration resistance to cancel that change, and to matching variable load resistances in the gain cell to correct for temperature-related and technology-related load-resistance errors.
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Lucent Technologies - Inc.
Tran Toan
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