Differential Transimpedance Amplifier Circuit for Correlated Differential Amplification

University of Arizona
posted on 06/04/2010

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Background:  When sensitive detectors are employed, their extreme sensitivity makes them sensitive to environmental factors that can produce undesirable electronic noise that obscures the true signal.  Examples of such environmental factors include: interfering electromagnetic waves, thermally-induced effects such as, thermally induced dark current, circuit and instrumental operating conditions, background radiation, and other random noise sources. When such noise due to environmental factors is present, its amplification can produce a total signal that is dominated by noise contributions rather than by the true signal that one desires to measure.

Invention:  A differential transimpedance amplifier circuit for correlated differential amplification has been realized. The amplifier circuit increases electronic signal-to-noise ratio in charge detection circuits designed for the detection of very small quantities of electrical charge and/or very weak electromagnetic waves. A differential, integrating capacitive transimpedance amplifier integrated circuit comprising capacitor feedback loops performs time-correlated subtraction of noise.

Advantages:  Higher detection sensitivity for weak signals, and less need for electromagnetic shielding.

Application:  Detection schemes for detection of ions, electrons, and other charged particles are especially susceptible to such environmental noise problems. Ion detectors are required in analytical instrumentation such as ion mobility spectrometers (IMS), ion mobility-based explosive and chemical-warfare-agent detectors, and mass spectrometers. Other applications of this invention are applicable to sensitive detection means for photodiodes, phototransistors, light detection arrays, and CMOS light detectors.

State of Development:  A US Utility Patent No.:  7,403,065 issued on Jul. 22, 2008. A prototype IMS device has been successfully demonstrated to detect explosive and small perfluorinated organic acids as vapors in ambient air. Work is continuing. OTT is looking for licensing or commercialization partners.

Lead Inventors: M. Bonner Denton and Roger P. Sperline