Carlos Christoffersen

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— Compact electrothermal modeling of lumped electrical devices and compact thermal modeling of volu-metric materials enables efficient electrothermal modeling of microwave circuits. The compact thermal model of the body of an X-band MMIC is based is based on analytical solutions of the heat diffusion equation in thermal sub-volumes. The model is(More)
This paper presents a practical implementation of an integrated MRI-compatible CMOS amplifier capable of directly driving a piezoelectric ultrasound transducer suitable for high-intensity focused ultrasound (HIFU) therapy. The amplifier operates in Class DE mode without the need for an output matching network. The integrated amplifier has been implemented(More)
—Two architectures for MOS-only low power voltage references with digitally-trimmable temperature coefficient are proposed in this work. A test chip implements them in a 0.35 µm CMOS process. A design methodology for both architectures, performance figures and preliminary test results are presented. Each circuit consumes around 4 nA and operates down to(More)
This paper presents for the first time an MRI-compatible integrated CMOS amplifier capable of directly driving a piezoelectric ultrasound transducer for High Intensity Focused Ultrasound (HIFU) applications. The amplifier operates in class DE mode loaded with a piezoelectric ultrasound transducer connected in parallel with a shunt capacitor. There is no(More)
A recently introduced wave-based transient analysis uses relaxation and thus does not require large matrix decomposi-tions at each nonlinear iteration. The use of waves results in guaranteed convergence for any linear passive circuit and some types of nonlinear circuits, but the convergence rate can not be controlled. In this work, the wave-based transient(More)
— Advances in communication hardware, urges a need for simulation tools, which can deal with large mixed signal circuits. For the first time, a transient circuit analysis using state variables, with high dynamic range is presented. The dynamic range of the analysis is experimentally verified by a two tone time domain simulation on a X-band MMIC.
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