A High Gain Operational Amplifier With Dual-Tail Source Architecture for Fast Slewing

This work introduces an enhanced operational amplifier architecture in which four flipped voltage follower (FVF) cells act as adaptive tail current sources to improve the performance of a conventional current mirror (CM)-based design. The FVF cells dynamically boost the differential pair current beyond the nominal bias level during the slewing interval, enabling a significantly higher slew rate and reduced settling time. By employing both n-channel and p-channel input stages driving cascode loads, the proposed dual FVF-controlled tail sources improve efficiency for both small- and large-signal operations. Additionally, the use of supplementary input devices increases the overall transconductance, thereby achieving higher DC gain and extended gain&#x2013;bandwidth product. The amplifier was implemented in TSMC 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m CMOS technology and validated through measurements, demonstrating a DC gain of 73.3 dB, a unity-gain bandwidth of 98.4 MHz, and a slew rate of 102.7 V/<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>s. The circuit operates from a 1.8-V supply, driving a 16-pF capacitive load, with a power consumption of <inline-formula> <tex-math notation="LaTeX">$642~\mu $ </tex-math></inline-formula>W.