Is it bootstrap circuit?

[qq91816]

Excuse me?

Whether there is bootstrapping principle on T15 T16 in this picture

Thank you very much.

 

[qq91816]

If it's bootstrapping, how does it work?

 

[forr]

T13 and T14 have their collector power supplies bootstrapped by T15 and T16.

The effet is that T13 and T14 Vce voltages see only small variations.

 

[knutn]

It is not any bootstrapping in this circuit.
However, the voltage variation in Q13 and 14 is small thanks to the cascode coupling of the output (with T13 and T14).