Why prefer to use the center tap???

[walid]

Often observed in many of the schemes that the circuit designer prefers to use the center tap as in Fig.(1) and not, as in Fig.(2), why?
 Thanks

[KevinIV]

Transformer's can be used in frequency resonant ciruits to allow for feedback. Their even ratio might be beneficial to the equation of oscillation, and there is no power consumption .

[walid]

I don't understand, please give me examples

[bassamfreiha]

Why prefer to uses in in frequency resonant for power.This design is very fantastic.There is no consumption.Many best example shoe in this cervical.