This paper presents a simple simplification method to design a multistage amplifier. The simplification procedure is based on a defined criterion which mainly related to ignoring negligible terms. In order to verify the validity and accuracy of the exploited method, a complex four‐stage CMOS amplifier is considered. Simplified transfer function and circuit simulator output are compared. According to simulation results obtained from HSPICE circuit simulator and TSMC 0.18 μm CMOS technology, the proposed approach expresses a bitter performance by 1% error. The aim is to propose a preprocessing algorithm. This helps main algorithm to deal with simpler inputs. In this way, a preprocessing algorithm is investigated which reduces CPU time and needed memory to simplify heavy symbolical transfer functions. Since target is analog and mix mode circuit, some circuit‐based assumptions are considered.

Multi-stage operational amplifiers are considered as basic building blocks in modern electronics since advanced Complementary metal-oxidesemiconductor (CMOS) technology limits exploiting cascode structures due to suffering from low voltage swings and the need of high gain capability. In this regard, an improved and high-performance three-stage CMOS amplifier is proposed in this work. The presented structure modeled mathematically and simulated via HSPICE circuit simulator with the 0.18-μm CMOS technology. An straightforward symbolic calculation is explained to obtain linear transfer function. According to the simulation results, the proposed circuit show 149 dB as DC gain while express 7.3 MHz and 380 μW as gain-bandwidth product and power dissipation, respectively. Such a high-performance amplifier has great potential to realize more complex analog and mixed mode signal systems such as modulators and data convertors.