Current-kink noise of n-channel enhancement e.s.f.i.-m.o.s. s.o.s. transistors

An experimental study of the low-frequency-noise properties of n-channel epitaxial silicon films on insulator m.o.s. s.o.s. transistors has been performed. The measurements show an excessive noise contribution at drain voltages corresponding to the current-kink effect for temperatures ranging from 4.2 to 300 K.     

Noise behaviour of the m.o.s.f.e.t. at v.h.f. and u.h.f.

The optimum noise figures of an m.o.s.f.e.t. at u.h.f. and at pinch-off are calculated using a simplified equivalent circuit. The noise parameters are also determined experimentally. Theory and experiment are shown to be in good agreement. Noise parameters of the m.o.s.f.e.t. for the frequency range 0.1?0.8 GHz are given.     

Performance of GaAs power m.e.s.f.e.t.s

Power performance results at 4 GHz are summarised for GaAs m.e.s.f.e.t.s ranging in size from 4 to 16 mm gate periphery. A double-chip 16 mm unit operated at 24 V source-drain bias produced 13.5 W with 3 dB gain and 10.7 W with 8.1 dB gain. Although lack of perfect power and gain scaling is observed, the degradation in output power of the 16 mm devices was only 1 dB compared to the smaller devices.     

Conversion gain of m.e.s.f.e.t. drain mixers

A theoretical analysis of the gain properties of m.e.s.f.e.t. drain mixers is presented. The m.e.s.f.e.t. model includes the nonlinearity of both the transconductance and the drain resistance. For a special case, a simple analytical expression for the gain is given. Numerical results for a typical example are briefly presented as an illustration.     

Subthreshold behaviour of e.s.f.i.-s.o.s. transistors

Theoretical and experimental results are presented which illustrate the influence of various parameters on the subthreshold behaviour of e.s.f.i.-s.o.s. transistors. The numerical analysis accounts for the thin silicon film and the existence of a second interface. A comparison is made with a corresponding bulk transistor, furthermore, between a two- and a one-dimensional analysis of e.s.f.i.-s.o.s. m.o.s.t. The agreement for real cases is found to be excellent.     

Analytical realisation of e.v.c.-a.r.c. networks

Consideration is given to the complete analytic solution of 3rd-order equal-valued-capacitor RC (e.v.c.-a.r.c.) networks due to Dutta Roy and Malik, and realisability limits are derived. The practically desirable cases of minimum resistor sum and minimum resistor spread are shown to occur at the same value of amplifier gain.     

New structure of enhancement-mode GaAs microwave m.o.s.f.e.t.

This letter proposes a new feasible device structure of an enhancement-mode GaAs deep-depletion m.o.s.f.e.t. as an attractive alternative to the junction-gate f.e.t.s and describes its microwave properties. The device has been fabricated on a high-resistance epitaxial n?-layer by simple readily available technology without requiring the sophisticated control of the channel thickness needed for the conventional junction-gate f.e.t.s. The 'normally-off nature of the device can be explained on the basis of the substrate space-charge region extending over then?-layer. The microwave performance of the device can be favourably compared with that of currently achievable junction-gate normally-off f.e.t.s. Unilateral gain drops to zero at a frequency slightly above 7 GHz.     

Substrate dependence of InP m.e.s.f.e.t. performance

There is evidence to suggest that Fe outdiffuses, during the growth, into the epitaxial films prepared by vapour-phase epitaxy at 650°C. Field-effect transistors on Fe-doped material show substantial looping that was absent on Cr-doped material and exhibit about 2 dB worse noise figure at about 7 GHz. Experiments with low 1015 S-doped InP grown on Sn-, Cr- and Fe-doped substates indicate that such outdiffusion is typically about 5 ?m. Saturation velocity levels in the m.e.s.f.e.t. channel are about 1.7 × 107 cm/s and 1.3 × 107 cm/s, associated with Cr and Fe doped substrates, respectively.     

White-light response of an m.o.s.t.

The photocurrent in an m.o.s.t. due to white-light illumination is studied. From the dependence of the photocurrent on the gate and drain voltages at different light intensities, the mechanisms responsible for the photocurrent are discussed.     

Efficient algorithm for determination of a.r. part of a.r.m.a. model

A fast recursive scheme is given for the solution of the Yule-Walker equations to obtain the a.r. part of an a.r.m.a. model. A lattice equivalent to the predictive filter is also included. This new structure requires what is subsequently called an adjoint model. The algorithm can be used in the evaluation of the a.r. and m.a. parsimonious orders.     

Decoding of b.c.h. codes

A new algorithm is given for the decoding of double-error-correcting binary b.c.h. codes. It can be rather simply implemented and is particularly suitable for parallel implementation.     

Load-line analysis of i.i.l.

A d.c. load-line analysis of i.i.l. structures is performed. Calculations are made of logic levels, noise margins and effective circuit parameters. Although the analysis is simple, it enhances the understanding of the circuit operation, and its predictions are in agreement with experiment and with more complicated analyses.     

Design of s.a.w. convolver for processing m.s.k. modulated waveforms

An acoustic waveguide convolver designed for matched filtering of m.s.k. modulated sequences with chirp period of 10.8 ns and with a processing gain of ~ 30 dB is reported. The device efficiency is ?63.5 dBm.     

O.M. v.p.e. growth of AlGaSb and AlGaAsSb

The epitaxial growth of AlGaSb and AlGaAsSb alloys by o.m. v.p.e. is reported. The growth technique and the dependence of the alloy composition on the input flux of gases are discussed.     

New estimate of the minimum noise figure of a m.e.s.f.e.t.

New estimates of the drain and gate noise multiplication parameters, the correlation coefficient and the minimum noise figure for a m.e.s.f.e.t. are advanced. For an uncooled GaAs m.e.s.f.e.t. having a 1 ?m gate length, a minimum possible noise figure of 1 dB at 10 GHz is predicted. InP is only marginally better.     

Pattern-recognition properties of r.a.m./r.o.m. arrays

Arrays of r.a.m.s may be used as trainable logic devices in arrays whose object is to recognise patterns. The way in which such a system is organised is presented and some of the characteristics of the nature of the recognition are discussed     

Direct modulation of d.h. GaAlAs lasers with GaAs m.e.s.f.e.t.s

GaAs m.e.s.f.e.t.s are used to directly modulate d.h. GaAlAs lasers with a 200 Mbit/s pseudorandom, return-to-zero bit stream. The detected light pulses have 100% modulation depth, no significant intersymbol interference, 40 mW of peak power and risetimes and falltimes of 240 ps for a halfpower width of 280 ps.     

Some effects of wave propagation in the gate of a microwave m.e.s.f.e.t.

In microwave field-effect transistors there is a progressive phase delay as a signal propagates along the gate, with a corresponding delay in channel modulation across the width of the transistor. It is shown that this leads to a phase lag in gm while the modulus of gm is comparatively unaffected.     

Realisation of three-valued c.m.o.s. cycling gates

A new design technique for three-valued cycling operators is presented. The new circuits are shown to be simpler than those previously reported.     

Effects of capacitance at crossover wirings in power GaAs m.e.s.f.e.t.s.

Power GaAs f.e.t.s. with an air-bridge crossover were compared with those of SiO2 crossover to find the effect of the capacitance at the crossover points. The capacitance of SiO2 crossover points is much smaller than that of the gate pad or the gate busbar in power GaAs f.e.t.s, and deterioration of the microwave performance due to that capacitance is negligible.