Q. Write a note on the application of emitter-follower?

An emitter follower can serve as a buffer for a voltage source. The voltage divider at left is a poor voltage source because it is so strongly affected by the value of the load resistor. The same voltage divider with the transistor buffer at right will supply power to keep the voltage constant over its range of operation.

The simple voltage divider will give a 4V output for an open circuit, but quickly drops when larger loads (smaller load resistors) are connected. The buffer helps to keep the output voltage more nearly constant. You can change the value of the load resistor below to explore the effect of the buffer.