Field-effect Transistor Amplifier Research Articles

Low-Noise Receiver Design Trends Using State-of-the-Art Building Blocks

The current state-of-the-art and the various design tradeoffs encompassing the variety of low-noise microwave and millimeter-wave receiver "building blocks" which have evolved during the past two decades are described. Key examples of these are the high-idler non-cryogenic parametric amplifier, the gallium arsenide field-effect transistor (GaAs FET) amplifier, and the image-enhanced Schottky-diode mixer. It is then shown how this inventory of building blocks can best be integrated into optimum receiver configurations for application in a multiplicity of future and present microwave and miltimeter-wave communications, RADAR, and radiometer systems.

Cryogenically Cooled GaAs FET Amplifier with a Noise Temperature Under 70 K at 5.0 GHz (Short Papers)

A 4.5-5.0-GHz gallium arsenide field-effect transistor (GaAs FET) amplifier cryogenically cooled to approximately 70 K is described. A noise temperature of under 70 K is achieved over the hand. Power gain for the two-stage amplifier is 20 dB. A noise analysis is performed to predict noise-temperature dependence on the temperature of the amplifier.

Input Amplifiers for Optical PCM Receivers

This paper describes the noise performance of input amplifiers for optical pulse-code-modulation repeaters. The noise is treated in terms of an effective noise generator in parallel with the photocurrent induced in the detector and the effective noise, in turn, is related to error performance. The analysis applies to both conventional and integrating front ends. Both field effect and bipolar transistor amplifiers are treated. For the latter, an optimum bias current that minimizes the effect of thermal noise is derived. Finally, predicted and measured performance are compared for silicon field-effect transistor input amplifiers at 6.3 Mb/s and 50 Mb/s, and for bipolar transistor and GaAs field-effect transistor input amplifiers at 274 Mb/s.

Methods of Reducing Noise of Junction Field Effect Transistor (JFET) Amplifiers

At present in non-dispersive X-ray spectrometers the electronic noise of the pulse amplifier input circuit prevents full realization of the inherent resolution of the semiconductor detector. Commercially available low noise JFET's encapsulated with boro-silicate (7052)glass insulated headers have typical noise contributions to detector resolution widths (FWHM), at 25°C, of 326 eV (Si). JFET's encapsulated with BeO or Al2O3 headers contribute ~200 eV to the resolution at 25°C and 150 eV at about -20°C. Techniques to select passive components which do not inhibit the performance of these transistors are discussed.

The frequency response characteristics of some condenser microphone infra-red detectors

The frequency response characteristics for interrupted infra-red radiation are described for four condenser-microphone type detectors as used in nondispersive infra-red gas analysers. Three of the detectors are of conventional dimensions. The fourth is a subminiature type, and its use is described with a field-effect transistor amplifier. It is shown that markedly increased optical modulation frequencies can be used with infra-red pneumatic detectors, without radical reductions in output signal, if the dimensions of the device are drastically reduced. This has been accounted for on theoretical grounds. The frequency responses obtained are examined and shown to correlate adequately with mathematically predicted profiles. Low frequency attenuation is explained on the grounds of thermal conductivity effects and leakage paths across the transducer diaphragm, whereas a high frequency maximum for one detector is shown to arise from Helmholtz resonation due to the chamber configuration.

Insulated gate field effect transistor amplifier.

Insulated gate field effect transistor amplifier.

Performance of a High Sensitivity Near Infrared Detection System

The performance of a synchronous detection system using a cooled phototube (type S1 cathode) is described. Detailed measurements including those using an ultralinear semiconductor photosource indicate that the system responds linearly within 1% per decade of incident flux variation. A tunnel diode discriminator increases the signal-to-noise ratio by a factor of up to 5. The over-all sensitivity obtained is ∼3×103 photons/sec or 5×10−16 W at 0.8 μ wavelength (phototube temperature −78°C). A field effect transistor amplifier with a relatively fast (390 cps) chopping rate is employed. In a spectrometer application in which the detection system is used in conjunction with a conventional monochromator (0.35 transmission, f/8 optics, and 0.005 μ/mm dispersion), a system sensitivity threshold of 4×10−12 W/cm2 μ sr is obtained at 0.8 μ wavelength.

Low noise solid state amplifiers for semiconductor detectors

The use of a tunnel diode and of a field effect transistor in the input stage of an amplifier for semiconductor detectors is discussed. The noise performance of the amplifiers is calculated and measured data are given. A simple and stable field effect transistor amplifier giving a resolution of 5 keV FWHM is described.