A Switched-Based Slew Rate and Gain Boosting Parallel-Path Amplifier for Switched-Capacitor Applications

A parallel-path amplifier (PPA) incorporating a switched-based slew rate and gain boosting stage as a feed-forward path, in parallel with a linear amplifier is introduced in this brief as an alternative to conventional analog amplifiers to achieve a high accuracy through the linear path and high slewing through the assisted feed-forward path. The feed-forward path employs a pre-amplifier, hysteresis-detector, and differential charge pumps, while the linear path includes a recycling folded-cascode amplifier. An analysis is performed to study the amplifier’s settling error with and without the feed-forward path, and also the trade-off between the dead-zone width of the hysteresis detector and the amplifier’s settling speed. The assisted feed-forward path has improved the slew rate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 2.5$</tex-math> </inline-formula>–800 V/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula>s, effective GBW by 15%, and dc gain by 16 dB at the expense of adding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$187.5~\mu $</tex-math> </inline-formula>A extra current consumption and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.25~\mu $</tex-math> </inline-formula>m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> extra silicon area. To prove the concept, the proposed amplifier is used as a multiplying digital-to-analog converter (MDAC) amplifier of an 8-bit pipeline analog-to-digital converter (ADC), and the ADC is fabricated in a 65-nm CMOS process. The results reveal that the spurious free dynamic range (SFDR) and signal-to-noise and distortion ratio (SNDR) performances are improved by 6–7 dB in the presence of the feed-forward path.