The concept of doctrine of power was introduced by Montesquieu, a French Scholar. He was opposed to concentration of power in one person and, hence, advocated vesting the state?s power in three organs of the state that is the legislature, the Judiciary, and the executive.
Separation of power in USA:
The doctrine of Separation of Power is the bedrock of the US constitution. All legislative powers, the executive powers and the judicial powers have been vested in the Congress, the President and the Supreme Court respectively. (Art 1, 2 and 3)
However, the separation of power is subject to doctrine of checks and balances, for example, a bill passed by the Congress can be vetoed by the President. Similarly, the Congress keeps a check over functioning of the executive through its various committees, and the Supreme Court has power to declare the laws passed by the Congress as unconstitutional.
Separation of power in India:
In India, separation of power is not practiced as strictly as in the USA. There is diffusion of executive and legislative persons.
Article 121: no discussion should take place in the parliament with regard to conduct of the judges of Supreme Court or high court in discharge of his duties.Article 361 provides immunity to the President and Governor. Article 50 puts an obligation over the state to separate the judiciary from the executive.
The doctrine of separation of power is basic feature of Indian constitution as per SC. there is not water tight compartmentalisation like US. But there are enough check and balances.