Maximum Available Gain Research Articles

Uniformity improvement of linear power pHEMTs using a very high selective wet etching

The realization and characterization of Al0.22Ga0.78As/In0.22Ga0.78As/GaAs multifinger linear power pHEMTs, using a citric acid selective wet etching for the gate recessing, are reported. A very high uniformity for both the drain current and pinch-off voltage values have been obtained. The linearity is confirmed by a quasiflat profile of the transconductance and of the maximum available gain (MAG) over a wide gate source voltage. Power and intermodulation distortion measurements at 16 GHz have been performed. An IP3 value of 25 dBm has been obtained for a 2×75 μm device. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 192–194, 1999.

Linearity Study on Enhance/Depletion Dual-Gate High Electron Mobility Transitors using Gain Mapping Method

Power gain linearity was studied using gain mapping method for enhance/depletion (E/D) dual-gate high electron mobility transistors (HEMTs). This method contains next steps; S-parameter and drain current were measured for all drain and gate voltage where interested. Maximum stable gain (MSG), maximum available gain (MAG) and H21 parameters were then calculated for frequency which is interested. These parameters were plotted on drain-current and drain voltage plane. By using this method into dual-gate HEMTs, it was found that threshold voltage of the second gates are essential for gain linearity and have its optimum value.

High-Performance HEMT with an Offset-Gate Structure for Millimeter-Wave Monolithic Microwave ICs

A process technology for a pseudomorphic high electron mobility transistor (P-HEMT) with an offset-gate structure has been developed for millimeter-wave monolithic microwave ICs (MMICs). A HEMT with the offset-gate structure showed both reduced gate-to-drain capacitance and drain conductance compared with a device with a non-offset-gate structure. The device showed a maximum available gain (MAG) of 9 dB at 77 GHz. The device was applied to a 77 GHz three-stage power amplifier, which showed a small-signal gain of 16.5 dB. Under preliminary life testing, this amplifier showed a stable small-signal gain for over 160 hours of testing at 175°C.

Invariance of S/sub 21//S/sub 12/ and K-factor under parallel operation of linear two-port devices

Based on a generalized circuit model for parallel-operated amplifiers with linear two-port devices, it has been proved that the S-parameter ratio S/sub 21//S/sub 12/ and hence MSG (maximum stable gain) are invariant as long as the devices have an identical value of S/sub 21//S/sub 12/ and the input and output networks are reciprocal. The invariance of K factor has been shown to hold for two cases: (i) devices are identical and input/output networks are lossless and symmetric with respect to each device, and (ii) identical admittances are added to the networks of case (i) so as to connect every device port with each other. Thus at least in these two cases, MAG (maximum available gain) and U (unilateral gain) are invariant as well as MSG under parallel operation of linear two-port devices. The invariance of S/sub 21//S/sub 12/ and hence MSG applies to a variety of parallel-operated amplifiers such as distributed amplifiers and linear power amplifiers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High-breakdown, high-gain InAlAs/InGaAsP quantum-well HEMTs

An investigation was conducted of the DC and RF characteristics of InAlAs/InGaAsP quantum-well channel HEMTs. An extrinsic transconductance as high as 210 mS/mm was obtained for a gate length of 1.0 mu m. The HEMTs showed excellent drain-source and gate-drain breakdown characteristics and a very small output conductance of less than 2 mS/mm, resulting in a very high DC voltage gain of greater than 100. The maximum available gain (MAG) was measured to be as high as 14.5 dB at 20 GHz, which corresponds to an extrapolated f/sub max/ of 105 GHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>