Voltage Clamp

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Johan Driesen - One of the best experts on this subject based on the ideXlab platform.

  • a fast Voltage Clamp circuit for the accurate measurement of the dynamic on resistance of power transistors
    IEEE Transactions on Industrial Electronics, 2015
    Co-Authors: Ratmir Gelagaev, Pieter Jacqmaer, Johan Driesen
    Abstract:

    For determining the dynamic on -resistance $R_{{\rm dyn},{\rm on}}$ of a power transistor, the Voltage and current waveforms have to be measured during the switching operation. The novel heterostructure wide-bandgap (e.g., AlGaN/GaN) transistors inherently suffer from the current collapse phenomenon, causing the dynamic on -resistance to be different from the static. Measuring Voltage waveforms using an oscilloscope distorts the characteristics of an amplifier inside the oscilloscope when the range of the measurement channel is not set wide enough to measure both on -state and off -state Voltage levels, resulting in failure to accurately measure the Voltage waveforms. A novel Voltage Clamp circuit improving the accuracy of the transistor's on -state Voltage measurement is presented. Unlike the traditional Clamping circuit, the presented Voltage Clamp circuit does not introduce delay caused by $RC$ time constants, keeping the Voltage waveform clear, even during state transitions of the device under test. The performance of the presented circuit is illustrated by measurements on a 2-MHz inverted buck converter.

  • A novel Voltage Clamp circuit for the measurement of transistor dynamic on-resistance
    2012 IEEE International Instrumentation and Measurement Technology Conference Proceedings, 2012
    Co-Authors: Ratmir Gelagaev, Pieter Jacqmaer, Jordi Everts, Johan Driesen
    Abstract:

    For determining the dynamic on-resistance R dyn,on of a power transistor, the Voltage and current waveforms have to be measured during the switching operation. In measurements of Voltage waveforms, using an oscilloscope, the characteristics of an amplifier inside the oscilloscope are distorted when the range of the measurement channel is not set wide enough to measure both on-state and off-state Voltage, resulting in failure to accurately measure the Voltage waveforms. A novel Voltage Clamp circuit improving the accuracy of the transistor on-state Voltage measurement is presented. The measurement accuracy is improved by Clamping the off-state Voltage across the transistor to a lower Voltage that is still greater than the on-state Voltage. Unlike traditional Clamping circuit, the presented Voltage Clamp circuit does not introduce delay caused by RC time constants keeping the Voltage waveform clear even during state transitions of the evaluated semiconductor device for frequencies up to 1MHz.

Riccardo Olcese - One of the best experts on this subject based on the ideXlab platform.

  • Cut-Open Oocyte Voltage-Clamp Technique
    2013
    Co-Authors: Antonios Pantazis, Riccardo Olcese
    Abstract:

    The cut-open oocyte Vaseline gap (COVG) Voltage Clamp technique, a relatively recent addition to the electrophysiologist’s armamentarium, was specifically developed by Drs. Stefani and Bezanilla (B ...

  • Voltage dependent conformational changes in human ca2 and Voltage activated k channel revealed by Voltage Clamp fluorometry
    Proceedings of the National Academy of Sciences of the United States of America, 2006
    Co-Authors: Nicoletta Savalli, Andrei Kondratiev, Ligia Toro, Riccardo Olcese
    Abstract:

    Large conductance Voltage- and Ca2+-activated K+ (BKCa) channels regulate important physiological processes such as neurotransmitter release and vascular tone. BKCa channels possess a Voltage sensor mainly represented by the S4 transmembrane domain. Changes in membrane potential displace the Voltage sensor, producing a conformational change that leads to channel opening. By site-directed fluorescent labeling of residues in the S3–S4 region and by using Voltage Clamp fluorometry, we have resolved the conformational changes the channel undergoes during activation. The Voltage dependence of these conformational changes (detected as changes in fluorescence emission, fluorescence vs. Voltage curves) always preceded the channel activation curves, as expected for protein rearrangements associated to the movement of the Voltage sensor. Extremely slow conformational changes were revealed by fluorescent labeling of position 202, elicited by a mutual interaction of the fluorophore with the adjacent tryptophan 203.

Shimon Marom - One of the best experts on this subject based on the ideXlab platform.

  • A 3-D approach to Voltage Clamp data
    Journal of Theoretical Biology, 1992
    Co-Authors: Shimon Marom
    Abstract:

    A simple transition from two-dimensional (2-D) handling of Voltage Clamp data to three dimensions (3-D), uncovered some stimulating relationships between the graphic representation of the I-V-t space of electrical activity of the membrane and physiological and biophysical functions of the plotted ionic currents.

Mark T. Harnett - One of the best experts on this subject based on the ideXlab platform.

  • Dendritic Spines Prevent Synaptic Voltage Clamp
    Neuron, 2017
    Co-Authors: Lou Beaulieu-laroche, Mark T. Harnett
    Abstract:

    Synapses are the fundamental units of information processing in the mammalian brain. Much of our understanding of their functional properties comes from Voltage-Clamp analysis, the predominant approach for investigating synaptic physiology. Here, we reveal that Voltage Clamp is completely ineffective for most excitatory synapses due to spine electrical compartmentalization. Under local dendritic Voltage Clamp, single-spine activation produced large spine head depolarizations that severely distorted measurements and recruited Voltage-dependent channels. To overcome these Voltage-Clamp errors, we developed an approach to provide new, accurate measurements of synaptic conductance. Single-synapse AMPA conductance was much larger than previously appreciated, producing saturation effects on synaptic currents. We conclude that electrical compartmentalization profoundly shapes both synaptic function and how that function can be assessed with electrophysiological methods.

H.r. Polder - One of the best experts on this subject based on the ideXlab platform.

  • Voltage-Clamp analysis of neurons within deep layers of the brain
    Journal of neuroscience methods, 1996
    Co-Authors: Diethelm W. Richter, O. Pierrefiche, Peter M. Lalley, H.r. Polder
    Abstract:

    Single electrode whole cell current- and Voltage-Clamp techniques in conjunction with intra- and extracellular phoresis and extracellular application of pharmacological agents were applied to study neurons in deep layers of the brainstem of anesthetized, paralyzed and artificially ventilated cats. We compared slow rhythmic changes and stimulus-evoked postsynaptic current and Voltage responses of neurons as they were recorded with fine-tipped microelectrodes filled with 2-3 M 'microelectrode solutions' or with 0.3 M 'patch solutions', or with patch electrodes. The experimental data were then compared with the effects of somatic and dendritic conductance changes simulated in a cell model. A new method was introduced for alternating current and Voltage-Clamp measurements performed at 300 Hz, which provided quasi-simultaneous measurements of slow changes of spontaneous synaptic currents and potentials. During current or Voltage Clamp, chemicals which affect Voltage- and receptor-controlled conductances were ionophoresed intracellularly through single or theta-type glass electrodes. We show examples of activation of low-Voltage activated Ca2+ responses after blockade of Na+ currents by intracellular QX 314 and K+ currents by intracellular Cs+ injections in addition to Sp-cAMPs to activate protein kinase A. TEA, NMDA and GABA were used to demonstrate the effectiveness of extracellular application of drugs through multibarrel electrodes or local application through a 'bath'. The various tests demonstrated that single electrode whole cell current- and Voltage-Clamp methods, in combination with various techniques for drug application, can be well applied to study the biophysical properties and pharmacological sensitivities of neurons embedded in in vivo networks within deep layers of the brain.