Fully Differential Operational Amplifier Design using Indirect and Negative Miller Compensation
This paper presents the design and analysis of a fully differential operational amplifier (op-amp). The amplifier architecture is based on the two-stage op-amp architecture with compensation around each amplification stage. The design operates on a +3.3 V single-rail power supply voltage operation and has been designed using a 0.35 μm CMOS technology. The consideration in choosing the internal compensation method was based on analysis of the op-amp’s frequency response and stability margins. To improve stability, indirect compensation is applied around the second stage of the amplifier architecture. To improve frequency response, negative Miller compensation is applied around the first stage with the aim to reduce the effect of the amplifier input capacitance. The other important influence on performance considered is temperature. The op-amp shows a better performance at lower temperatures whereas the performance reduces at higher temperatures.The design was simulated with a variation of temperature in the range of -40°C to 125°C. The validation strategy was based on simulation using typical, worst-case power andworst-case speed device models using the Cadence Spectre circuit simulator.
Index Terms- Fully differential,indirect compensation, negative Miller compensation, temperature.