Servo Push Pull power amp?

[Castillovanv]

Is this a push pull arrangement or what is it called?

The X crossing pattern is a push pull arrangement?

Because Q25 goes to Q29 WHY?
Why does Q26 goes to Q28?

Is this some type of push pull arrangement or what?

 

[chuckey]

Its a badly drawn H bridge. The output 4 transistors are actually two pairs, each one capable of swinging from earth to +28 V. So redraw the output transistors as two vertical pairs, one each side of the motor. now the Q25/Q26 cross over becomes obvious as the diagonal pairs of output transistors must be switched on at the same time.
Frank

 

[Castillovanv]

Why do servo motors need an H bridge driver? What does the crossover connection do? If no crossover connection what will happen?

 

[chuckey]

If you have a 24V PSU, then just using a single ended driver will give you +24V on one end of the motor and either 0V or 24 V on the other so a total voltage drive of 24V. If you use a H bridge, at one instance the motor gets a 0V on terminal A and +24V on terminal B, then +24 V on terminal A and 0V on terminal B, i.e. the motor will have 48 V of drive on it.
With no cross over the motor will not run, because there will be a current path to the 0V line but both the transistors going to the +24V line will be switched off.
Frank

 

[kam1787]

http://www.talkingelectronics.com/projects/H-Bridge/H-Bridge-1.html