FIG. 7 demonstrate the fast settling of a low noise amplifier, reducing it from ?18 s to 110 ms at the initial system startup. The amplifier core power is 70 nW and clock generation power is 62 nW shared over two amplifiers. The measured transfer characteristics for a chain of amplifier (e.g., LNA+PGA) are also shown in FIG. 8 for different gain configurations. Overall, SAFR maintains similar amplifier specifications for noise, harmonic distortion, and performance as compared to its pseudo-resistor version. Accurate control of the high pass corner permits the use of the amplifier in many biomedical applications and guarantees reliable performance across a wide range of temperatures and process variation.

FIG. 9 is a schematic for a differential amplifier circuit 90 which uses a sample and average feedback resistor in both feedback paths. The differential amplifier 92 has an inverting input, a non-inverting input, a first output, and a second output. A first feedback path 93 is formed between the first output of the amplifier circuit and the inverting input of the amplifier circuit; whereas, a second feedback path 94 is formed between the second output of the amplifier circuit and the non-inverting input of the amplifier circuit.