Test

Push-Pull Follower

If we put two emitter followers together (npn transistor for positive voltages; pnp transistor for negative voltages), we get a push-pull follower.

If $V_{in}$ > 0.7V, then the current is amplified by the npn transistor.

If $V_{in}$ < -0.7V, then the current is amplified by the pnp transistor.

and -0.7V, because the voltage has not pass the cutoff voltage for either transistor. This is known as crossover distortion.