AD2S1210 excitation buffer question

Henry,

Unfortunately I did not design the output stage on the evaluation board so I don't have intimate knowledge of why the original designer chose to go bipolar instead of using MOS but I fundamentally don't see an issue with using FETs for the output stage.   The only thing I can think of is that ultimately BIPOLAR devices may have allowed for a smaller more cost effective design with respect to achieving the desired current drive.  I will see if I can track down a more definitive answer for you and respond if I find out anything of interest.

Sean

Sean,

Thanks for the note.  another question is that i noticed that the eval board has a DC bias up to 5.7v (2.5v ref + 3.75v on inverted input of opamp).  i can see why it was designed like this so that the output signal can be centered around 6v for +12v to 0v driving.  My question is whether i should put the ac-decoupling cap at the output to the resolver excitation coil? 

do you see any need for that?

Thanks,

Henry

Henry,

I do not see the need for any AC coupling between the driver and the resolver primary.

Sean

BJTs may give an advantage to limiting output current should one of your resolver wires be cut, shorted or mis-wired.