Application of FEI's in Temperature Compensation of DC Amplifiers

Hanna, Nabil N.

doi:10.1109/tim.1979.4314756

Cited by 2 publications

(1 citation statement)

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“…Junction field-effect transistors (JFET's) have been used by some investigators to compensate for the temperature drift in de amplifiers [2]. However, MOSFET's are superior to JFET's due to their very high-input impedances.…”

Section: Introductionmentioning

confidence: 99%

Application of MOSFET's in the temperature compensation of DC amplifiers

Rizkalla

Hanna

1987

IEEE Trans. Instrum. Meas.

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ss where cPf substrate fermi potential, Cox oxide capacitance per unit area, V BS substrate-to-source bias, /leff effective mobility, l channel length, w effective channel width, cPMS metal semiconductor work function difference, N substrate doping, q electron charge, E s permittivity of silicon, and V ss voltage equivalent of the equivalent interface charges.Assuming N / C~x « 1 transfer characteristics are given by of both linear and nonlinear devices was studied. The theoretical and experimental results obtained in these investigations were used in the design of high-input impedance dc amplifier, in which a good overall drift performance is obtained by using a MOSFET biased at nearly zero ternperature coefficient. The MOSFET· bias is adjusted to provide a drift in the main amplifier. The completecircuit is described and the adjustment procedure is outlined. II. OPERATION OF LINEAR DEVICESThe temperature characteristics of MOSFET devices in the saturation region is given by (1) Abstract-A new application of metal oxide silicon field-effect transistor (MOSFET) devices for solving the problem of drift in the characteristics of de amplifiers under the effect of temperature variations in the range of 20-75°C is presented. Expressions for the bias voltages and drain currents for operation at zero temperature coefficient for linear and nonlinear devices were derived. The validity of the derived expressions were checked experimentally for various samples of MOS-FET's. These expressions were used to design the MOSFET stage to compensate for the drift of the dc amplifier. The amplifier has proved to be very reliable and can be adjusted for practically zero drift over a narrow band of temperatures. The drift was about 40 f.1V/°Cover the range of 20-75°C and about 10 f.1V /°C over the range of 50-70°C. The 3-dB point in the frequency response is about 1.7 MHz. The overall gain is about 750 and the amplifier is capable of supplying a peakto-peak output voltage of 3.0 V.

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Section: Introductionmentioning

confidence: 99%