In the paper, we present a design of a low voltage Operation Amplifier (OPAMP) circuit using split-length transistors. Indirect feedback compensation is an advanced technique used to stabilize the operation of an OPAMP. Cascode transistors are usually implemented for indirect feedback systems. However, these transistors are not suitable for low voltage design. In this study, we have taken advantage of split-length transistors and indirect feedback compensation technique to design a high performance OPAMP. As a result, the OPAMP operates not only at low supply voltage but also at high frequency. The OPAMP has been designed and fabricated in a 0.18um CMOS technology. This OPAMP achieves 100 dB gain, 90 MHz unity gain frequency and 60 degrees phase margin at 2 V supply voltage.
A design of low voltage OPAMP using split-length transistors
