To provide an operational amplifier which can operate with no offset over an entire range of power voltage by performing the independent adjustment of input offset between the N and P channel transistor top type differential amplifier circuits.

When the input voltage applied to a plus input terminal 54 is kept within a prescribed range, the P channel transistors TR 22, 23, T3 and T4 of a P channel TR top type differential amplifier circuit 20 are turned off and only an N channel TR top type differential amplifier circuit 10 operates. When the input voltage applied to the terminal 54 is kept in another prescribed range, the N channel TR 12, 13. T1 and T2 of the circuit 10 are turned off and only the circuit 20 operates. As a result, the offset trimming operations of both circuits 10 and 20 can be carried out independently of each other.