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Browse Prior Art Database

Inductor Arrangement for Maximum External Noise Rejection

IP.com Disclosure Number: IPCOM000114586D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Thompson, GA: AUTHOR

Abstract

This disclosure describes a method to reduce external magnetic field coupling into inductors connected to differential amplifiers. This method utilizes a unique inductor arrangement and circuit wiring in order to minimize circuit magnetic field susceptibility.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Inductor Arrangement for Maximum External Noise Rejection

      This disclosure describes a method to reduce external magnetic
field coupling into inductors connected to differential amplifiers.
This method utilizes a unique inductor arrangement and circuit wiring
in order to minimize circuit magnetic field susceptibility.

      Inductors are often required for filtering and for DC biasing
in many analog signal-processing applications.  Unfortunately,
inductors can receive external noise from nearby magnetic field
sources, and that can adversely affect overall circuit operation.
This disclosure describes a component wiring technique for minimizing
unwanted noise coupling to inductor pairs connected to a differential
amplifier.  This technique can reduce noise pick-up in order to
supplement, or perhaps even reduce, the amount of magnetic field
shielding required.

      Inductor components wired to the inputs of a high-gain
differential amplifier pose a difficult design challenge when noisy
magnetic field sources are close by.  For example, consider the
circuit shown in Fig. 1.  In this application, surface-mount
inductors provide DC bias for a transducer that is AC-coupled to a
differential amplifier.  The inductors should play no other role than
to isolate the low-impedance voltage source(s) from the
high-impedance
amplifier inputs.  Unfortunately, if noisy magnetic field sources are
nearby, these inductors will behave as transducers themselves and
contribute a noise voltage to the desired signal voltage.

      Since the inductors are physically-separate components on the
circuit board, it is possible for them to be exposed to different
magnetic field levels depending upon how each are positioned with
respect to the external magnetic field source.  Because magnetic
field levels decrease rapidly with increasing distance from the
so...