Wide Bandwidth Class-S Power Amplifiers for Ultrasonic Devices

Abstract

Wide bandwidth ultrasonic devices are a necessity in high-resolution ultrasonic systems. Therefore, constant output voltages need to be produced across the wide bandwidths of a power amplifier. We present the first design of a wide bandwidth class-S power amplifier for ultrasonic devices. The −6 dB bandwidth of the developed class-S power amplifier was measured at 125.07% at 20 MHz, thus, offering a wide bandwidth for ultrasonic devices. Pulse-echo measurement is a performance measurement method used to evaluate the performance of ultrasonic transducers, components, or systems. The pulse-echo signals were obtained using an ultrasonic transducer with designed power amplifiers. In the pulse-echo measurements, time and frequency analyses were conducted to evaluate the bandwidth flatness of the power amplifiers. The frequency range of the ultrasonic transducer was measured and compared when using the developed class-S and commercial class-A power amplifiers with the same output voltages. The class-S power amplifiers had a relatively flat bandwidth (109.7 mV at 17 MHz, 112.0 mV at 20 MHz, and 109.5 mV at 23 MHz). When the commercial class-A power amplifier was evaluated under the same conditions, an uneven bandwidth was recorded (110.6 mV at 17 MHz, 111.5 mV at 20 MHz, and 85.0 mV at 23 MHz). Thus, we demonstrated that the designed class-S power amplifiers could prove useful for ultrasonic devices with a wide frequency range.

A Class-J Power Amplifier Implementation for Ultrasound Device Applications

“…The maximum applied voltages of these small-size transducers are quite limited, so that effective power transfer could be more preferable to stabilize performance [32]. The previously developed class-S power amplifier has wide bandwidth to be covered for wideband ultrasonic transducer [29]. However, class-J power amplifier was designed to have high output power with high efficiency.…”

“…On the other hand, a class-E power amplifier was developed for 41.5 kHz piezoelectric ultrasonic transducers in favor of a specific frequency ranges [23,27]. Since the sensitivity of an ultrasound system generally depends on the voltage or power gain of the device, it is useful for the power amplifier of the ultrasound device to be a high-voltage or high-power amplifier [28,29]. A class-J power amplifier, boasting the advantages of high power and efficiency, have been used in telecommunication baseband systems [30,31].…”

Wireless Ultrasound Surgical System with Enhanced Power and Amplitude Performances

“…By comparing the before and after re-poling processes, sharp impedance characteristics are shown, where the calculated Q m value increased approximately 2 times to minimize heat generation because the bandwidth is related to power consumption [ 58 , 59 ].…”

Novel Bandwidth Expander Supported Power Amplifier for Wideband Ultrasound Transducer Devices

“…This circuit is added to the circuit, as shown in Figure 3, and thus the amplifier performance by applying different constant DC voltages is changed depending on the MOSFET (M1, BSS123) operation. When this circuit is assumed to be an ideal current source or ideal switch, the DC bias voltage VB1 in the BWE circuit operates the transistor, M1, as described below [36][37][38]: In ultrasonic diagnostic equipment, the frequency of the input signal and the cycle of the burst wave were adjusted such that the Q factor used for providing an appropriate image quality was calculated [1]. Assuming that the LDMOSFET operates in the saturation region, the changes in the pole and transfer function can be estimated.…”