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Circuit applied for the low-frequency noise measurements. The dashed square indicates the low-frequency equivalent circuit of an antenna-coupled CMOS detector with its high-frequency equivalent circuit presented in the zoom area. Note: The capacitances Cgd (21 fF) used as an AC shunt at 620 GHz can be neglected below 1 GHz since their impedance at these frequencies exceeds 8 MΩ.
Response of a CMOS detector to 330-Hz electronically chopped 620-GHz radiation as a function of the DC bias current, measured at gate voltages Vg ranging from 0.5 to 0.7 V. Inset: static I/V characteristics at the same gate voltages. All fitting lines are calculated by Eqs. (1) and (3) with the same set of parameters.
RC-roll-off-corrected spectral density of the drain voltage fluctuations for near-zero bias (circles), (squares), and (diamonds) for a gate voltage of 0.58 V. Black lines represent fits taking into account thermal noise and excess noise (including both 1/f and generation-recombination noise “gr”), with their relative contributions at indicated by dashed lines. Inset: Measured data . The drain voltage was varied in steps of 20 mV.
Calculated (dashed lines) and measured (points) SNR values at a modulation frequency of 200 kHz, normalized to the maximum value obtained at V without bias current. Inset: measured bias dependence of signal (lines) and amplitude of voltage fluctuations (data points) for several modulation frequencies at V.
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