Modify two stage OPAMP based on offset constellation technique

The main objective behind this proposed design is to reduce the low offset voltage for the minimum value, so that its effect is reduced by two stage CMOS operational amplifier. The majority of operational amplifiers mainly consist of two inputs and one output. The signal coming out from the amplifiers is a description of the distinction and comparison between any two input signals that are independent on each other. Practically no voltage appears on the output and the offset voltage is close to zero in the event that there is no difference between the two input signals. In this paper, comprising two proposed circuits are designed and simulated using OrCAD PSpice 17.4, first, a circuit consisting of two stages is designed for a 180 nm technology operational amplifier, a designed two-stage amplifier circuit consisting of eight semiconductor switches (MOSFET). Second, a proposed circuit consist of a two stage OPAMP in conjunction with an auxiliary OPAMP. In the two proposed circuits, the MOSFET parameters are designed and excellent results obtained, including reduction of offset voltage and preservation of the gain value, where the offset voltage value of the Two-stage circuit was 71 µv and the offset value of the proposed design was equal to 21 µv as the offset voltage was improved and reduced by 70 %.