An Auto-Zero-Stabilized Voltage Buffer With a Quiet Chopping Scheme and Constant Sub-pA Input Current

This article describes an auto-zero stabilized voltage buffer that achieves low offset and noise with sub-pA input current. A high gain stabilization loop is used to periodically cancel the buffer’s offset. The itself disconnected from auto-zeroed, during which its bandwidth reduced reduce associated folding. However, this also reduces correction range, so avoid overloading, initial digitally trimmed. To break up correlation between residual low-frequency (LF) of phases, chopped, significantly LF noise. Finally, duty-cycle two phases optimized bring density close $\sqrt {2}$ times white (14 nV/ {\text {Hz}}$ ), fundamental limit AZ amplifier. a constant current (0.8 pA), as well state-of-the-art (0.4 notation="LaTeX">$\mu \text{V}$ ).