Difference between revisions of "Electronics written problems"
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For each of the circuits in the previous problem, find two equivalent circuits — the first one consisting of a single ''voltage'' source and a single resistor, and the second one consisting of one ''current'' source and one resistor. In both equivalent circuits, the I-V curve at the V<sub>out</sub> the port should be identical to the original circuit. | For each of the circuits in the previous problem, find two equivalent circuits — the first one consisting of a single ''voltage'' source and a single resistor, and the second one consisting of one ''current'' source and one resistor. In both equivalent circuits, the I-V curve at the V<sub>out</sub> the port should be identical to the original circuit. | ||
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|[[File:High pass filter.png|350px]] | |[[File:High pass filter.png|350px]] | ||
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+ | ==Measuring action potentials== | ||
+ | [[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 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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+ | * 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'' <math>\left( \frac{V_{patch}}{V_{noise}} \right )^2</math> of the measurement? | ||
+ | * 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. | ||
+ | }} | ||
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Revision as of 19:16, 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. 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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