Difference between revisions of "Electronics written problems"
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==Measuring action potentials== | ==Measuring action potentials== | ||
[[File:Patch clamp circuit model.png|thumb|right|Circuit model of a patch clamp (not including capacitance).]] | [[File:Patch clamp circuit model.png|thumb|right|Circuit model of a patch clamp (not including capacitance).]] | ||
− | The [https://en.wikipedia.org/wiki/Patch_clamp patch clamp] is a technique for measuring voltages produced by electrically active cells such as neurons. A circuit model for a neuron connected to a patch clamp apparatus consists of a time-varying voltage source in series with an output impedance of 10<sup>11</sup> Ω. There is an oscilloscope next to the neuron with an ''input impedance'' of 10<sup>6</sup> Ω. A | + | The [https://en.wikipedia.org/wiki/Patch_clamp patch clamp] is a technique for measuring voltages produced by electrically active cells such as neurons. A circuit model for a neuron connected to a patch clamp apparatus consists of a time-varying voltage source in series with an output impedance of 10<sup>11</sup> Ω. There is an oscilloscope next to the neuron with an ''input impedance'' of 10<sup>6</sup> Ω. A simple model for the oscilloscope is a 10<sup>6</sup> Ω resistor to ground. A new UROP in the lab attempts to measure the electrical spikes produced by the neuron (called ''action potentials'') using the oscilloscope. The oscilloscope has a noise floor of 10<sup>-3</sup> V. |
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Revision as of 02:13, 18 October 2018
This is Part 2 of Assignment 6.
Ideal elements
Solving circuits
For each of the circuits below, find the voltage at each node and the current through each element. |
Equivalent circuits
Measuring action potentials
The patch clamp is a technique for measuring voltages produced by electrically active cells such as neurons. A circuit model for a neuron connected to a patch clamp apparatus consists of a time-varying voltage source in series with an output impedance of 1011 Ω. There is an oscilloscope next to the neuron with an input impedance of 106 Ω. A simple model for the oscilloscope is a 106 Ω resistor to ground. A new UROP in the lab attempts to measure the electrical spikes produced by the neuron (called action potentials) using the oscilloscope. The oscilloscope has a noise floor of 10-3 V.
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- What is the magnitude of the signal the student measures after connecting the oscilloscope?
- Does the student succeed? Why or why not?
- What is the signal to noise power ratio $ \frac{V_{patch}^2}{V_{noise}^2} $?
- How many times does the student curse during the measurement attempt?
- What is the minimum input impedance that a measurement device must have in order to make a high-fidelity measurement of an action potential.
Simple Bode plots
Harder Bode plots
Linear systems