Design of a Wide-Band Voltage-Controlled Ring Oscillator Implemented in 180 nm CMOS Technology

The design of a wide-band voltage-controlled oscillator (VCO) modified as a VCO with programmable tail currents is introduced herein. The VCO is implemented by using CMOS current-mode logic stages, which are based on differential pairs that are connected in a ring topology. SPICE simulation results show that the VCO operates within the frequency ranges of 2.65–5.65 GHz, and when it is modified, the VCO with programmable tail currents operates between 1.38 GHz and 4.72 GHz. The design of the CMOS differential stage is detailed along with the symbolic approximation of its dominant pole, which is varied to increase the frequency response in order to achieve a higher oscillation frequency when implementing the ring oscillator structure. The layout of the VCO is described and pre- and post-layout simulations are provided, which are in good agreement using CMOS technology of 180 nm. Finally, process, voltage and temperature variations are performed to guarantee robustness of the designed CMOS ring oscillator

Left atrial myxoma irrigated by the right coronary artery: an unusual presentation form

Los tumores cardíacos se dividen en primarios y secundarios. A su vez, los tumores primarios pueden clasificarse en benignos y malignos. Los más frecuentes son los benignos y más del 50 % de los casos corresponden a los mixomas, que pueden ser asintomáticos o presentar una amplia variedad de manifestaciones clínicas, en dependencia de su localización y tamaño. El diagnóstico clínico se sospecha ante la auscultación de un “plop tumoral” y debe corroborarse con estudios de imagen; el ecocardiograma es el tipo de estudio de primera elección y el tratamiento definitivo, la resección quirúrgica del tumor. Se reporta el caso de un paciente masculino, quien presentó un evento vascular cerebral isquémico de etiología cardioembólica. El ecocardiograma evidenció una tumoración en la aurícula izquierda, compatible con un mixoma, que recibía irrigación a través de las ramas de la arteria coronaria derecha, lo cual constituye un caso inusual.Cardiac tumors are divided into primary and secondary. Primary tumors in turn are classified in benign and malignant. Benign tumors are more frequent, and more than 50 % of the cases are myxomas which, depending on their location and size, could be asymptomatic or present a wide range of clinical manifestations. The clinical diagnosis is suspected upon auscultation of a tumor plop and must be corroborated with imaging studies. The echocardiography is the study of first choice, and the surgical resection of the tumor is the definite treatment. The case of a male patient with a cerebrovascular ischemic event of cardioembolic etiology is reported. The echocardiography showed a tumor in the left atrium, compatible with myxoma, which received irrigation through the branches of the right coronary artery, which is an unusual case