Figure 5.

Measured Bode magnitude plot with the gain of both channels set at 60 dB (a) and input-referred noise (b) of the Chebyshev notch channel (red line) and the Bessel notch channel (blue line). (a) Both channels provide a passband between 0.5 and 500 Hz. The roll-off of the high- and the low-pass filters equals +20 dB/decade and −40 dB/decade, respectively, for both topologies. However, the Chebyshev notch channel provides a sharper transition between the passband and the stopband and stronger attenuation at the central frequency of the notch (=140 Hz), compared to the Bessel notch channel. Besides, the Chebyshev notch channel exhibits a flat magnitude response in the passband and approximates the magnitude response of the Bessel notch channel. (b) Based on the input-referred noise graph, it is concluded that both channels are low-noise with the Chebyshev notch channel presenting a slightly better noise performance. Noise power spectral density estimates in the passband for the Chebyshev and the Bessel notch channels are 4 nV ${(\sqrt{\text{Hz}})}^{-1}$ and 4.4 nV ${(\sqrt{\text{Hz}})}^{-1},$ respectively, with the residual 1/f corner estimated at roughly 10 Hz for both channels.