A low voltage and low power Operational amplifier (Opamp) using Process, temperature insensitive current source has been presented. The design methodology of the addition based current source and the Opamp implementation using this current source is presented. The spice simulations are carried out in GPDK 90 nm technology at 0.6 V supply. The results of addition based current source Opamp are compared with the MOSFET current source Opamp. The proposed Opamp shows better gain of 80.6db, GBW of 3MHz and low power consumption of 54 uW.