To verify the proposed concept, pulse-echo responses from an ultrasonic transducer were tested with the developed class-C power amplifier using a resistor divider and the designed diode expander architecture. Thus, the proposed architecture could increase the input pulse amplitudes applied to the main transistors in the power amplifiers, hence increasing the output voltage of such amplifiers. To overcome this issue, we propose a new diode expander architecture dedicated to power amplifiers to reduce the effects of sinusoidal pulses toward the power supply. However, class-C power amplifiers generate less output power, resulting in a reduction of system sensitivity.
Non-linear power amplifiers, such as class-C amplifiers, could substitute linear power amplifiers, such as class-A amplifiers, which are currently used in point-of-care ultrasound systems. However, the excessive heat generated from ultrasound transmitters has an impact on the implementation of piezoelectric transducer elements and on battery consumption, thereby affecting the system’s sensitivity and resolution. 2001.Point-of-care ultrasound systems are widely used in ambulances and emergency rooms. Gaier et al., “Power-amplifier modules covering 70–113 GHz using MMICs”, Transactions on Microwave Theory and Techniques, Vol. Tayrani, “A monolithic X-band class-E power amplifier”, GaAs IC Symposium, pp. Staudinger, “An overview of efficiency enhancements with applica-tion to linear handset power amplifiers", IEEE RFIC Symposium, pp. Sokal, “Class-E – a new class of high efficiency tuned single-ended switching power amplifiers”, IEEE Journal on Solid-State Circuits, Vol. Simburger et al., “A monolithic 2.5V, 1W silicon bipolar power amplifier with 55% PAE at 1.9GHz”, Microwave Theory and Techniques Symposium, pp. Johnston, “Transformer coupled stacked FET power amplifiers”, IEEE Journal on Solid-State Circuits, Vol. Raab, “Class-F power amplifiers with maximally flat wave-forms”, IEEE Transactions on Microwave Theory and Techniques, Vol. Sokal, “Transistor power losses in the class E tuned power amplifier”, IEEE Journal on Solid-State Circuits, Vol. Raab, “Idealized operation of the class-E tuned power amplifier”, IEEE Transactions on Circuits and Systems, CAS-24, pp. Mertens, “A 700 MHz fully differential CMOS Class-E power amplifier” Journal of Solid State Circuits, Vol. Raab, Solid-state Radio Engineering, Wiley, New York, 1980. Kenington, High-linearity RF Amplifier Design, Artech House, 2000.
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