An Enhanced Scheme of Multi-Stage Amplifier With High-Speed High-Gain Blocks and Recycling Frequency Cascode Circuitry to Improve Gain-Bandwidth and Slew Rate

With the existing circuit topologies, the conventional multi-stage amplifiers (MSA) can only achieve low gain-bandwidths (<;5 MHz) and low slew rates (<;10 V/μs). These specifications are not satisfied by most operational amplifier (OPA) related circuit designers. To solve this issue, a novel enhanced scheme of multi-stage (ESMS) amplifier is proposed by this study. The scheme of the proposed ESMS includes a recycling frequency cascade (RFC) amplifier with a shunt current source and high-speed current mirrors, a high-speed block (HSB), and a high-gain block (HGB). Briefly, the circuitry mechanism of the ESMS amplifier demonstrates two key functions. Firstly, when an input signal is feeding into the first stage, the RFC amplifier along with the shunt current source and the current mirrors, play an important role to enhance the slew rate. Secondly, as the signal goes to the consecutive stage, low and medium frequency signals go through to the direct-coupled high-gain block (HGB), and the high-frequency signal goes to the high-speed block (HSB). Thus, the total DC gain and gain-bandwidth are improved. To test the gain-bandwidth and slew rate characteristics, the proposed ESMS amplifier was simulated by using a TSMC 0.18-μm CMOS process standard technology with a 1.8 V power supply. The results of the experiment showed that when driving a 5-pF/1-kΩ load, the proposed ESMS amplifier achieved 105.5 dB DC gain, 231.77 MHz gain-bandwidth, and 13.25 V/μs average slew rate. Compared to the NMC amplifier, one of the most well-known conventional MSAs, the proposed ESMS amplifier boosted the gain-bandwidth by 55.32 times and improved the average slew rate by 1.55 times.