LEFT: High input impedance is affecting the voltage across the 200 ohm load. An op-amp in the voltage follower configuration ensures that Vout = Vin regardless of the input impedance.
RIGHT: Voltage divider is drastically affected by the load resistance of 200 ohms. By using the op-amp in a voltage follower configuration, we again ensure that the load voltage is equal to the Vout of the divider circuit regardless of the load resistance.
