Baxandall transdiode question

[scoobis]

In a Quasi-complementary output stage when your using a Baxandall transdiode, should it be the same transistor used for the positive driver.

i've seen examples where the transistor used was not the same and it seems to me that in order to best emulate the characteristics of the positive driver it should be the same transistor as the positive driver.... or am i off base here...

 

[Mark Tillotson]

No, that's likely to give best symmetry according to Baxandall - a transdiode is better than a diode, but either will improve the symmetry of cross-over and reduce the sharp discontinuity of the quasi-complementary topology (which is otherwise the worse class B arrangement, generating many harmonics positive and negative, as there isn't a good bias point).


CFP outputs use a much lower bias current than EF outputs, and combined them in the quasi-complementary arrangements is responsible for the worse behaviour - no bias current is optimal. The diode helps make the CFP side much more like an EF and thus permits more balanced biasing.