Infra‐Red Instrumentation and Techniques

https://science.sciencemag.org/content/sci/110/2860/414.full.pdf

The Cortical Correlate of Pattern Vision.

A low-noise CMOS instrumentation amplifier intended for low-frequency thermoelectric microsensor applications is presented that achieves submicrovolt offset and noise. Key to its performance is the chopper modulation technique combined with a bandpass filter and a matching on-chip oscillator. No external components or trimming are required. The achievable offset performance depends on the bandpass filter Q and the oscillator-to-bandpass filter matching accuracy. Constraints are derived for an optimum Q and a given matching accuracy. The improvement of common-mode rejection ratio (CMRR) in chopper amplifiers is discussed. The amplifier features a total gain of 77/spl plusmn/0.3 dB and a bandwidth of approximately 600 Hz. The measured low-frequency input noise is 8.5 nV//spl radic/Hz and the input offset is 600 nV. The measured low-frequency CMRR is better than 150 dB. The circuit has been implemented in a standard 1-/spl mu/m single-poly CMOS process.

A fully integrated, untrimmed CMOS instrumentation amplifier with submicrovolt offset

An experimental procedure is described for measuring dichroism in the infra‐red spectrum of oriented materials. Oriented films of polythene, polyvinyl alcohol, polyvinyl chloride, polyvinyl acetate, and Nylon have been examined in the region 3600–700 cm−1, and the species (parallel or perpendicular) of many bands has been identified. The bearing of these results on current ideas concerning the structure of these polymers is discussed. A general result is that frequencies involving the motion of hydrogen atoms show rather low dichroism. On the other hand, very high dichroism has been found in some frequencies in which the motion is believed to be confined to other atoms.

Polarized Infra‐Red Radiation as an Aid to the Structural Analysis of Long‐Chain Polymers. I

Determination of Oxygenated and Olefin Compound Types by Infrared Spectroscopy

The electronic amplifier, described herein, is designed to measure extremely small d.c. and low frequency a.c. voltages in low impedance sources. Expressing the electrical noise in terms of equivalent input voltage with a 5‐ohm input resistance and a 5‐milliamp. Esterline‐Angus recorder, the maximum departure from the mean does not exceed 1.5×10−9 volt. Under laboratory conditions the drift is less than 5×10−9 volt over a period of 8 hours. The amplifier is compact and rugged, and it is not affected by vibrations or accelerations experienced in moving vehicles. At present the amplifier is employed in the measurement of radiant energies in infra‐red spectrographs. It is also used for various laboratory and field measurements.

C. E. Quinn

Papers

A Contact Modulated Amplifier to Replace Sensitive Suspension Galvanometers