![]() ![]() To recapitulate: This is a three-stage MMIC power amplifier that utilizes HEMTs as gain elements. The amplifier chip was described in "MMIC HEMT Power Amplifier for 140 to 170 GHz" (NPO-30127), NASA Tech Briefs, Vol. Figure 1 shows the resulting amplifier module. To facilitate separate testing, it was decided to package the amplifier and doubler chips in separate waveguide modules. While it was feasible to connect the amplifier and frequency-doubler chips by use of wire bonds, it was found to be much more convenient to test the amplifier and doubler chips separately. The amplifier chip was needed for driving a high-electron-mobility-transistor (HEMT) frequency doubler. Power-Amplifier Module for 145 to 165 GHzĪ power-amplifier module that operates in the frequency range of 145 to 165 GHz has been designed and constructed as a combination of (1) a previously developed monolithic microwave integrated circuit (MMIC) power amplifier and (2) a waveguide module. The table summarizes the performances of the three stages The input signal can range from -10 to +10 dBm into a 50-ohm load. Each stage contains a pair of GaAs-based field-effect transistors biased in class D. The amplifier includes an input, a driver, and a final stage. Another major novel feature is a transmission-line power splitter/combiner designed with the help of phasing techniques to enable an approximation of a square-wave signal (which is inherently a wideband signal) to propagate through what would, if designed in a more traditional manner, behave as a more severely band-limited device (see figure). The design incorporates state-of-the-art switching techniques applicable only in the microwave frequency range. In order to design this amplifier, it was necessary to derive mathematical models of microwave power transistors for incorporation into a larger mathematical model for computational simulation of the operation of a class-D microwave amplifier. In addition, relative to class-A amplifiers, class-D amplifiers are less likely to go into oscillation. ![]() Relative to the traditional classes A, B, and C of amplifier operation, class D offers the potential to achieve greater power efficiency. In the ideal case of zero "on" resistance, infinite "off" resistance, zero inductance and capacitance, and perfect switching, the output signal would be a perfect square wave. ![]() Nominally, in class D operation, a transistor is switched rapidly between "on" and "off" states so that at any given instant, it sustains either high current or high voltage, but not both at the same time. Class-D operation has been utilized at lower frequencies, but, until now, has not been exploited in the S band. High-Efficiency Microwave Power AmplifierĪ high-efficiency power amplifier that operates in the S band (frequencies of the order of a few gigahertz) utilizes transistors operating under class-D bias and excitation conditions. The noise power spectrum density was of type 1/f and extended to 10 kHz. In performance evaluations, the input-referred voltage noise was 4 μVrms/Hz0.5 at 1 Hz and 30 nVrms/Hz0.5 at 10 kHz, respectively. The gain-bandwidth product can expect 400 kHz at a power dissipation of 6 μW. The amplifiers operate at 4.2 K with an open-loop gain of 2000. Based on our experience with these cryogenic ICs, we designed, manufactured, and demonstrated operational amplifiers requiring four power supplies and two voltage sources. To realize a multipixel camera for astronomical observation, we developed cryogenic multi-channel readout systems using gallium arsenide junction field-effect transistor (GaAs JFET) integrated circuits (ICs). Hibi, Yasunori Matsuo, Hiroshi Ikeda, Hirokazu Fujiwara, Mikio Kang, Lin Chen, Jian Wu, Peiheng Amplifier consists of battery- powered operational amplifier coupled by means of light-emitting diodes to another amplifier which may be grounded and operated from ac power mains or separate battery supply.Ĭryogenic ultra-low power dissipation operational amplifiers with GaAs JFETs Possibility of shocks from leakage currents can be reduced by use of isolated preamplifiers. ![]()
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