Carlos Christoffersen

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A low-voltage, ultra-low-power sub-threshold proportional to absolute temperature (PTAT) current source is proposed. The new topology generates the PTAT current from the ratio between the drain currents of two transistors in subthreshold operation. Linearity is analyzed and a compensation strategy to improve it is developed. This is the first time such a(More)
A recently introduced wave-based transient analysis uses relaxation and thus does not require large matrix decompositions 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)
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)
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)
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 0.95(More)
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