Output impedance

About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.

Millimeter-wave active probe

Abstract: A millimeter-wave active probe for use in injecting signals with frequencies above 50GHz to millimeter-wave and ultrafast devices and integrated circuits including a substrate upon which a frequency multiplier consisting of filter sections and impedance matching sections are fabricated in uniplanar transmission line format. A coaxial input and uniplanar 50 ohm transmission line couple an approximately 20 GHz input signal to a low pass filter which rolls off at approximately 25 GHz. An input impedance matching section couples the energy from the low pass filter to a pair of matched, antiparallel beam lead diodes. These diodes generate odd-numberd harmonics which are coupled out of the diodes by an output impedance matching network and bandpass filter which suppresses the fundamental and third harmonics and selects the fifth harmonic for presentation at an output.

A switched-capacitor RF front end with embedded programmable high order filtering and a +15dBm OB-B1dB

Abstract: A 0.1–0.7GHz switched-capacitor RF front end features tunable center frequency and programmable filter order as well as very high tolerance for out-of-band (OB) blockers. RF input impedance matching, N-path filtering, down-conversion, and high order IIR filtering are implemented using highly linear switches and capacitors only. The 3.24mm2 40nm CMOS front-end prototype consumes 38.5–76.5mA, achieves 24dBm OB-IIP3 and 14.7dBm B1dB for a 30MHz offset, 6.8 to 9.7dB NF, and >66dB calibrated harmonic rejection ratio.

Self-Tuning LCC Inverter Using PWM-Controlled Switched Capacitor for Inductive Wireless Power Transfer

Abstract: Wireless power transfer with a self-tuning LCC inverter using pulsewidth modulation (PWM) controlled switched capacitor is proposed in this paper in order to compensate for the variations of Tx inductance. Usually, receivers contain magnetic and conductive materials for shielding and mechanical support. The inductance of the Tx coil is sensitive to the variation of Tx–Rx alignment because the interaction between the Tx coil and the Rx magnetic–conductive materials is also varied. It is shown that the detuning of the Tx inductance value exacerbates the losses in the LCC inverter. In the proposed method, the PWM duty ratio of a single capacitor adjusts the effective output impedance of the LCC inverter. The PWM feedback loop is designed such that the power factor and the real-part impedance of the LCC inverter are maximized. The PWM switch is turned on at zero voltage and turned off with low dv / dt , minimizing switching losses. Such a soft-switching tunable capacitor can handle higher power compared to the traditional hard-switching capacitor, p-n junction capacitor, or an analog IC capacitor. Another advantage of the proposed technique is the continuity in achievable capacitance value using only one capacitor. The feedback can be fully implemented by analog components, obviating the necessity of digital samplings, ADC/DACs, and microcontrollers. The power of 54 W is transferred at 76.6% and 60.7% with and without the proposed method, respectively.

Source-gated transistors in hydrogenated amorphous silicon

Abstract: Source-gated transistors form a new class of transistors in which the current is controlled entirely by the source. As such, they have properties that are fundamentally different from their nearest relative the field-effect transistor. Instead of using the field-effect to modulate the conductance of a channel it is used to change to electric field at a reverse biased source barrier thereby changing the source current. Saturation of the current occurs when the source is depleted of carriers by the reverse biased barrier. This feature contrasts markedly with saturation in a standard field-effect transistor that occurs when the drain end of the channel is depleted of charge. A model describing the characteristics of a source-gated transistor is outlined and compared with characteristics measured on transistors made using hydrogenated amorphous silicon. Good agreement is found between theory and experiment. It is shown that the saturation voltage of the SGT can be very much smaller than it is in a FET leading to lower voltage operation and power dissipation. Furthermore, the output impedance of the SGT can exceed that of an FET. Transistors covering a wide range of currents have been made by modifying a Schottky barrier source using ion implantation.

Design and characterization of a high-power ultrasound driver with ultralow-output impedance

Abstract: We describe a pocket-sized ultrasound driver with an ultralow-output impedance amplifier circuit (less than 0.05 ohms) that can transfer more than 99% of the voltage from a power supply to the ultrasound transducer with minimal reflections. The device produces high-power acoustical energy waves while operating at lower voltages than conventional ultrasound driving systems because energy losses owing to mismatched impedance are minimized. The peak performance of the driver is measured experimentally with a PZT-4, 1.54 MHz, piezoelectric ceramic, and modeled using an adjusted Mason model over a range of transducer resonant frequencies. The ultrasound driver can deliver a 100 V(pp) (peak to peak) square-wave signal across 0-8 MHz ultrasound transducers in 5 ms bursts through continuous wave operation, producing acoustic powers exceeding 130 W. Effects of frequency, output impedance of the driver, and input impedance of the transducer on the maximum acoustic output power of piezoelectric transducers are examined. The small size, high power, and efficiency of the ultrasound driver make this technology useful for research, medical, and industrial ultrasonic applications.