rectifier question

[texane]

hi,

on the following schema, I have trouble understanding
what the d3 and d4 diode paths are used for...

If I create the same schema without those paths, I get
the same voltage (I am plotting the curves with ngspice
actually) between n1 and vdd.

Thus, do you have any idea what those paths are for?

Cheers,

t.

[armandas]

Thus, do you have any idea what those paths are for?

No, unless you upload the schematic

[texane]

hu, sorry, a bit tired

[armandas]

You need to imagine where the current flows when voltage across V1 is positive and when it's negative.
In the positive cycle, current flows through D2 and D4, in the negative cycle - through D1 and D3.

I'm not quite sure how it works with two diodes only

[armandas]

Regarding the same voltage:

I just created this circuit in LT SPICE and it seems that ground is affecting the voltage source by forcing 0V on the negative side. Check your waveforms.

[jimmc]

This is the standard bridge rectifier, as armandas has implied V1 must float.
D1 or D2 connect whichever end of V1 is more positive than n0 at any given instant to n0,
D3 or D4 connect whichever end of V1 is more negative than Vdd at any given instant to Vdd.

By the way the normal convention is Vdd is the positive rail and Vss the negative.

Jim