Multi-channel neural signal amplifier system providing high CMRR across an extended frequency range

A method for detecting, sensing, or recording, or amplifying biopotentials across multiple biopotential amplifier channels using a biopotential amplifier having (a) an input stage comprising a plurality of inputs and a plurality of outputs, the input stage comprising a reference low noise amplifier (LNA) and a plurality of signal LNAs, the plurality of signal LNAs comprising a signal LNA corresponding to each channel of the multiple biopotential amplifier channels (b) a second stage comprising a plurality of signal inputs, at least one reference input, and a plurality of outputs, and (c) a common mode feedback (CMFB) signal generator comprising a plurality of inputs coupled to the plurality of input stage outputs and a set of outputs, the method comprising:

• receiving a biopotential signal corresponding to each channel of the multiple biopotential amplifier channels at an input of a signal LNA corresponding to the channel, each signal LNA for a given channel of the multiple biopotential amplifier channels including an input, an output, a supply terminal (LNAVDD terminal), and a ground terminal (LNAVSS terminal);
• receiving a reference signal at a reference input of the reference LNA of the input stage, the reference LNA including an input, an output, a supply terminal (LNAVDD terminal), and a ground terminal (LNAVSS terminal);
• coupling signals output by the signal LNAs to corresponding signal inputs of a second stage amplification and/or processing unit of the second stage;
• coupling a reference signal output by the reference LNA to at least one reference input of the second stage signal amplification and/or processing unit;
• coupling signals output by each signal LNA and the reference signal output by the reference LNA to the inputs of the CMFB signal generator;
• generating a set of CMFB signals with the CMFB generator corresponding to the signals provided to the CMFB signal generator inputs;
• and
• providing supply rail based CMFB (SR-CMFB) to the input stage by feeding back the set of CMFB signals to at least one of the LNAVDD terminal and the LNAVSS terminal of each signal LNA and the reference LNA.