http://www.badongo.com/pic/4653103

What will the waveforms of the output voltages look like in these circuits A, B and C? Does the polarity of Vi play any role?

 

Is Vi an AC voltage source?

Do you assume that the diodes are ideal?

 

Yes, the diodes are ideal. Their turn on voltage is 0.7 V. Vi = Vosin(wt)=5sin(wt)

I assume circuit A will clamp voltages lower than - 0.7 V, while for circuit B the output will be clamped to +- 0.7 V? No idea when it comes to C though.

 

Circuit A will clip voltages greater than 0.7 volts
Circuit B will clip voltages greater than 0.7V and less than -0.7V
Circuit C will clip voltages greater than 2.7V and less than -2.7V

 

Circuit A will clip voltages greater than 0.7 volts
Circuit B will clip voltages greater than 0.7V and less than -0.7V
Circuit C will clip voltages greater than 2.7V and less than -2.7V

Circuit C will clip voltages greater than 2.7V and less than 1.3V.
This was homework. We should have asked to see the OP's answers first.

 

Thanks RonH for the correction, i was not very careful.

 

Circuit C will clip voltages greater than 2.7V and less than 1.3V.

You mean greater than 2.7V and less than -1.3V?

 

No, he meant just what he posted. You might get some useful knowledge by looking into the conduction characteristic of a diode.