Output impedance

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

High frequency cautery electric power source device

Abstract: A high frequency cautery electric power source (1), which is set in a processing device, applies high frequency electric power to processing electrodes when excision is started under electrically conductive liquid. When an output impedance detected at its application time is lower than a set value, a variable direct current power source circuit (HVPS) is set to a constant current control mode, so that high frequency electric power including an instantaneously high voltage value is intermittently applied to start discharge while output current is limited to the fixed. When the output impedance becomes or is higher than the set value, a constant voltage control mode is set, so that power with predetermined voltage is supplied and the cautery treatment is carried out by means of high frequency current suitable for subject living body.

Method and apparatus for determining internal impedance of animal body part

Abstract: Apparatus and a method for determining the internal impedance of a portion of an animal body. Two electrical currents of different frequencies are passed through the body portion and the voltage across the body portion corresponding to each current flow is sensed. In-phase coherent detection is performed to remove the out-of-phase signal components and the resulting in-phase voltage signals are subtracted from each other to yield a measure of only the internal impedance of the body portion. The invention is especially suitable for use in measuring the changes in the amount of fluid in the human lung.

High-drive CMOS output buffer with noise supression using pulsed drivers and neighbor-sensing

Abstract: A CMOS output buffer has a first stage with smaller driver transistors and a second stage having larger driver transistors. Both stages drive the output in parallel during the first half of a voltage transition, but the larger, second stage is disabled during the second half of the output voltage swing. The output voltage is fed back to an isolation circuit by a pulse generator which is triggered by the output reaching the switching threshold. The pulse generated disables the larger driver for a short period of time but later re-enables the driver. Thus the large driver remains on after the switching is complete, providing large IOH and IOL static currents. The pulse is long enough to keep the large driver disabled while reflections are received and ringing occurs after the voltage transition. Resistors in the smaller first stage absorb these reflections. The output impedance is pulsed to the higher impedance of the first stage when ringing occurs at the end of the voltage transition, but after the pulse ends the lower impedance of the large driver is seen. Pulses are sent to neighboring output buffers and are OR'ed together to disable adjacent output buffer's large drivers when noise in injected into the power or ground supplies.

Impedance controlled output driver

Abstract: An output driver has an output multiplexor and an output current driver. The output multiplexor receives a data signal and outputs a q-node signal. The output current driver receives the q-node signal and drives a bus based on the q-node signal. The output multiplexor processes the data signal in various ways to generate the q-node signal. The output current driver is responsive to current control bits to select a amount of output drive current. In addition, the output multiplexor is controlled such that the output impedance of the output current driver is maintained within a predetermined range.

Electrical Impedance Tomography of brain function

Abstract: Electrical impedance tomography is recently developed imaging technique, with which images of the internal impedance of the subject can be rapidly collected with rings of external ECG - type electrodes. It is fast, inexpensive, portable and is very sensitive to physiological changes which affect the electrical impedance properties. Set against this is a relatively poor spatial resolution and ill posed nature of the procedure for reconstructing images, such that a small errors due to instrumentation translate into large errors in images. For about two decades, satisfactory images have been obtained of changes over time related to gastric emptying and ventilation and cardiac output in the thorax. The main work of the speakerpsilas group has been to adapt existing EIT designs for the demanding application of imaging changes in the brain due to conditions like stroke, epilepsy or normal physiological brain activity; the difficulty is that the skull is resistive and diverts current so that the signal to noise ratio is low. In addition, imaging of acute stroke requires one-off images where the use of time difference to correct for instrumentation errors is not possible. Approaches used to overcome these problems include the use of signal processing, improved numerical models for image reconstruction, and the use of frequency difference imaging.