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Consequently, higher input voltage signals could affect the bias circuit operation for class-C power amplifiers. However, class-C power amplifiers produce a relatively lower voltage gain compared to class-A power amplifiers and also consume a lower DC current. Therefore, the bias circuits in class-A power amplifiers would be less affected by input pulse signals. In ultrasound instruments, the maximum allowable input voltages are generally limited to 1 V p–p.
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Therefore, class-A power amplifiers can use relatively lower input voltage signals compared to class-C power amplifiers. Class-A amplifiers produce a higher gain compared to class-C power amplifiers while consuming a higher DC current. Therefore, the proposed class-C power amplifier with diode expander architecture is a potential candidate for improving the sensitivity performance of piezoelectric transducers for point-of-care ultrasound systems.ĭiode expanders placed after power amplifiers have originally been used to reduce unwanted ring down signals generated from class-A power amplifiers in ultrasound instruments. The peak-to-peak amplitude of the echo signals of the ultrasonic transducers when using a class-C power amplifier with a diode expander architecture (2.98 V p–p) was higher than that for the class-C power amplifier with a resistor divider architecture (2.51 V p–p). 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. Low physical size for given Power output.Point-of-care ultrasound systems are widely used in ambulances and emergency rooms.It consumes low power and improves the efficiency of the wireless communications.ĭesigning a Class-C Power Amplifier(PA) at 865MHz frequency. Here, Class-C PA design is discussed along with the actual implementation using CMOS technology within the Cadence software. The efficiency of class-C power amplifier varies from 50% to 85%. It is also better than other options when it comes to large scale integration. Using CMOS technology here reduces cost, hence it is used in building many integrated systems. Power amplifiers are used at different places which have a lot of applications. It amplifies a signal to high power that ensures a transmitted signal to propagate across some distance and be received at the receiver end. A power amplifier is a final block in the transmission path of a transceiver.