Absnact: Self-aligned GaAs JFET narrowband amplifiers operating at 2.4GHz were designed and fabricated with both discrete JFETs as a hybrid amplifier and as RFICs. Enhancement-mode JFETs were used in order to be compatible w i t h complementary digital logic. Hybrid amplifiers achieved 8-10 dB of gain at 2.4 GHz and 1 mW DC bias level. The RFIC achieved 10 dB of gain at 2 4 GHz and 2 mW DC bias level.Introduction: Low power circuitry is very important for battery powered e1e:ctronic components. While low power operation of digital circuitry is taken for granted due to the unique advantages offered by CMOS architecture, microwave circuits have no equivalent low power circuit configuration, require quiescent bias, and consequently have been reported infrequently in the literature. Commercial GaAs MESFET foundry technology was used to design and fabricate an amplifier with 15dB of gain for 2-stages with 0.8 mW power at 1.25 GHz [l]. An HFET (heterostructure field effect transistor) amplifier RFIC (radio frequency integrated circuit) achieved 10 dB of gain at 0.5 niW and 900 MHz [2]. Amplifiers that operate at the 1 m W power level or lower have not been reported previously at higher frequencies. Microwave gain and return loss measurements were performed using an HP 8510C network analyzer using Cascade Microtech microwave probes calibrated using a TRL calibration. S-parameters were measured at wafer level and used to design a narrow-band 2.4 Experimental Hybrid AmplifierGHz microsmp based amplifier. Amplifiers were fabricated on Rogers TMM-10 25 mil thick substrates. The measured gain vs. frequency is plotted in Figure 2 far three amplifiers using chip and wire assemblies. Peak gains between 8 and 10 dB were measured at 2.4 GHz and 1 mW DC power.JFET RFIC: The hybrid amplifier was subsequently redesigned and fabricated as a RFIC with on-chip matching. The chip dimensions are 2.8 x 2.3 mm2. After fabrication the RFIC was silver epoxied to a metal substrate along with chip capacitors for bias stability and alumina microsmp circuit adapters to facilitate microwave probing. The W l C was designed for off chip bias control of the gate and drain so that it could be tested under various bias conditions. Shown in Figure 3 are plots of the gain (10 dB peak at 2.45GHz, and input/output return loss (< -15 dB at 2.45 GHz) all measured at 2 mW I>C bias condition (VDS = 2 V, ID = 1 mA). At 1 mW the gain drops to 7-8 dB. Good agreement with the earlier hybrid amplifier and the RFIC design goals was achieved. 3Conclusion: Low power microwave technology results have been presented for 0.7 pn GaAs JFETs which are compatible with a digital CHFET technology. Both discrete and RFIC amplifiers were demonstrated which achieved 8-10 dB of gain at 2.4 GHz with 1-2 mW of DC power consumption. Acknowledgments:The authors would like to thank Geraldine Lopez, Melissa Cavaliere,
This report summarizes work on the development of ultra-low power microwave CHFET integrated circuit development. Power consumption of microwave circuits has been reduced by factors of 50-1000 over commercially available circuits. Positive threshold field effect transistors (nJFETs and PHEMTs) have been used to design and fabricate microwave circuits with power levels of 1 milliwatt or less. 0.7 pm gate nJFETs are suitable for both digital CHFET integrated circuits as well as low power microwave circuits. Both hybrid amplifiers and MMlCs were demonstrated at the 1 mW level at 2.4 GHz. Advanced devices were also developed and characterized for even lower power levels. Amplifiers with 0.3 pm JFETs were simulated with 8-10 dB gain down to power levels of 250 microwatts (pW). However 0.25 pm PHEMTs proved superior to the JFETs with amplifier gain of 8 dB at 217 MHz and 50 pW power levels but they are not integrable with the digital CHFET technology.
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