Power driver for operational amplifiers

It happens frequently that the output current of an operational amplifier is inadequate for the application as, for instance, whent a small motor or loudspeaker has to be driven. Normally, this is resolved by adding an emitter follower to the circuit as shown. Unfortunately, that circuit does not allow the fuIl supply voltage, Ub, to be uscd, because the output voltage of the opamp must always be 1-2 V smaller than ±Ub. To that must be added the drop across the base-emitter junction of transistors Tl and T2.