Difference between revisions of "Electronics written problems"
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==Measuring action potentials== | ==Measuring action potentials== | ||
− | + | 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 and an input capacitance of 20 pFd. A new UROP in the lab attempts to measure the electrical spikes produced by the neuron (called ''action potentials'') by connecting a patch-clamped neuron to the oscilloscope with a cable that has a capacitance of 80 pFd. The oscilloscope has a noise floor of 10<sup>-3</sup> V. | |
− | 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 | + | File:Patch clamp circuit model.png|750px]] |
{{Template:Assignment Turn In|message= | {{Template:Assignment Turn In|message= | ||
− | * | + | * Neglecting the capacitance, what is the magnitude of the signal the student measures after connecting the oscilloscope? |
* Does the student succeed? Why or why not? | * Does the student succeed? Why or why not? | ||
− | * What is the ''signal to noise power ratio'' <math>\left( \frac{V_{patch}}{V_{noise}} \right )^2</math> of the measurement? | + | * What is the ''signal to noise power ratio'' <math>\left( \frac{V_{patch}}{V_{noise}} \right )^2</math> of the measurement (neglecting the capacitance)? |
+ | * Assuming V<sub>neuron</sub> is a 1 ms, square pulse of magnitude 100 mV, sketch V<sub>neuron</sub> and V</sub>scope</sub>. (You may neglect the oscilloscope's resistance.) | ||
* How many times does the student curse during the measurement attempt? | * How many times does the student curse during the measurement attempt? | ||
− | * | + | * Ignoring capacitance, what is the minimum input impedance that a measurement device must have in order to make a high-fidelity measurement of an action potential. |
}} | }} | ||
{{Template:20.309 bottom}} | {{Template:20.309 bottom}} |
Revision as of 19:48, 18 October 2018
This is Part 2 of Assignment 6.
Ideal elements
Resistive circuits
For each of the circuits below, find the voltage at each node and the current through each element. |
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Equivalent circuits
Easy Bode plots
Harder Bode plots
Linear systems
Measuring action potentialsThe 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 and an input capacitance of 20 pFd. A new UROP in the lab attempts to measure the electrical spikes produced by the neuron (called action potentials) by connecting a patch-clamped neuron to the oscilloscope with a cable that has a capacitance of 80 pFd. The oscilloscope has a noise floor of 10-3 V. File:Patch clamp circuit model.png|750px]]
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