It is often necessary in practical applications to connect op amp circuits in cascade to achieve a large overall gain.
A cascade connection is a head-to-tail arrangement of two or more op amp circuits such that the output of one is the input of the next.
When op amp circuits are cascaded, each circuit in the string is called a stage; the original input signal is increased by the gain of the individual stage.
Since the output of one stage is the input to the next stage, the overall gain of the cascade connection is the product of the gains of the individual op amp circuits.
\(\displaystyle A = A_1 \cdot A_2 \cdot A_3\)