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# Diodes and Path of Current

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Sketch the path of the current through the diodes when the voltage is as given for the two cases shown (see attached file for full problem description). If the voltage drops across each diode is 0.7V, what is the current through the resistor in each case? Finally, use the bridge circuit shown and design a DC power supply for a 12-V AC signal with a ripple voltage less than 0.4V. Sketch your circuit.

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#### Solution Preview

Dear student,

Please see the attached jpg scan. To find the value for C which willgive 0.4 V ripple, we argue as follows: We assume the load current is whatever is drawn by the 200 kOhm resistor, because we're not told otherwise. Also, when someone says "12 VAC", they usually mean RMS, so the peak voltage is the square root of two (1.414) times 12 = 17.0 V. Call the AC voltage "VAC". Call the peak AC voltage Vp. So Vp = VAC X 1.414.

NOW CHECK THIS IN YOUR TEXT OR WHATEVER - IT MIGHT BE THAT YOUR INSTRUCTOR MEANS 12 V PEAK. IF HE DOES, THEN USE 12.0 WHEREVER I HAVE USED 17.0 BELOW!!!
In that case the value for C comes out to 1.16 uF.

Assuming Vp = 17.0 V:
The maximum voltage across C will be
Vp - 0.7 V = 16.3 V. This means that ...

#### Solution Summary

This solution contains a sketch of the path of current through the diodes with annotations accompanied with clear explanations to determine the current in each resistor.

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