I'm given a full bridge rectifier circuit with values for power, industance, and RMS input voltage: [P = 380 W, L = 85 uH, Vs = 115 V].

Full Bridge

The question states to 'select' output resistance for a simulation, but I am unsure if it's possible to calculate this. It might be that it is asking to select an arbitrary number.

I'm guessing that it can be calculated using:

$$ R = V_s^2/P = 34.8 \varOmega $$ I am wondering if the voltage drop across the inductor can be omitted at steady state. Is this the correct way one would determine the load resistance?


Assuming negligible losses in the inductor and rectifier and a low value for C, your calculation is good.

As the source is 115V I'm assuming the frequency is 60Hz, so L has a reactance of 0.032Ω - insignificant compared to R. Assuming silicon diodes with suitable ratings the rectifier should be dropping about 1.4V - again an insignificant amount.

The capacitor is a wild card - if large enough to hold the voltage up between peaks then DC output voltage could get close to 160V, and R might have to be much higher (67Ω?).


Or you could just read the number on the resistance. It's not the output impedance you are looking for but the value of the load resistor.

  • \$\begingroup\$ This doesn't seem helpful, it looks like a theory question rather than measuring the value from a physically built circuit. \$\endgroup\$ – PeterJ Jan 20 '15 at 2:19

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