## 3 Simulation Results  
### Simulated Results Using the Equivalent Circuit Model for a Dry Electrode-Skin Interface  
A photograph of the layout of the proposed circuit is shown in Figure 8. The proposed circuit was designed using 0.18-\(\upmu\)m bipolar-complementary metal semiconductor-double-diffused metal oxide semiconductor (BCDMOS) technology. The active area of the proposed circuit is 1.8 mm\({}^{2}\). A simulation of the setup for ECG monitoring that considers dry electrode-skin contact is shown in Figure 9. For simulation of the ECG monitoring, an ECG/PLI signal generator, a capacitive coupling for PLI, and an equivalent circuit model of the dry electrode-skin interface were used [14]. The word \"subcutan\" expressed in Figure 9 is a shortened form of \"subcutaneous\". The simulated total power consumption is 18 \(\upmu\)W and the current-reus  
Figure 8: A photograph of the layout of the proposed circuit. Simulated results of the transient response at the ECG input and the differential output with and without the proposed PLI reduction circuit are shown in Figure 10. The gain of the current-reused CFIA is 40.55 dB. Figure 10a shows the raw ECG signal, including PLI with or without the proposed PLI reduction circuit. Without the proposed PLI reduction circuit, the saturation effect of the ECG input is caused by the PLI through the ESD diode. However, with the proposed PLI reduction circuit, the ECG input is clamped with BIAS_P and BIAS_N, and the saturation effect does not occur. Figure 10b shows the amplified ECG signal by the current-reused CFIA according to the presence or absence of the proposed PLI reduction circuit. Abnormal ECG amplification occurs when the proposed PLI reduction circuit does not exist, but if the proposed PLI reduction circuit does exist, normal ECG amplification is possible. Simulated results of the input-referred noise of the current-reused CFIA are shown in Figure 11. The input-referred root mean square (RMS) noise of the current-reused CFIA has 2.68 \(\mu\)V\({}_{\text{RMS}}\) with the 107 Hz of bandwidth. Figure 10: Simulated results of the transient response at the ECG input and output node before and after PLI clamping: (**a**) the ECG input voltage including PLI, (**b**) the output differential voltage amplified by the current-reused CFIA. Figure 9: Simulated setup for ECG monitoring considering dry electrode–skin contact. Simulated results of the CMRR of the current-reused CFIA are shown in Figure 12. The measured CMRR is above 105 dB, and the mid-band gain measures 40.5 dB with a bandwidth of 107 Hz. A performance summary and comparison of the proposed circuit is shown in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Parameter** & **This Work** & **Ref. [9]** & **Ref. [10]** & **Ref. [11]** & **Ref. [13]** \\ \hline Supply voltage & 1.8 V & 1.2 V & 1 V & 1.3–1.8 V & 2 V \\ Technology & 0.18 \(\upmu\)m & 0.18 \(\upmu\)m & 0.065 \(\upmu\)m & 0.18 \(\upmu\)m & 0.35 \(\upmu\)m \\ Power consumption & 18 \(\upmu\)W & 27.8 \(\upmu\)W & 2.1 \(\upmu\)W & 680 nA & 320 nW \\ PLI limiting & Yes & Yes & No & No & No \\ Type & CFIA & CCIA & CCIA & CCIA & CCIA \\ Input impedance & \textgreater{}10 GO 1 & - & 20–80 MO & \textgreater{}400 M\(\Omega\) & 20 M\(\Omega\) \\ Current consumption & 185 nA & - & 2.1 \(\upmu\)A & 150 nA & 160 nA \\ \multirow{2}{*}{IA} & Mid-band gain & 40.5 dB & 35 dB & 40 dB & - & 39.8 dB \\ Bandwidth & 107 Hz & 100 Hz & 100 Hz & 130 Hz & 200 Hz \\ Input-referred RMS & 2.68 \(\upmu\)V\({}_{\text{RMS}}\) & 5.05 \(\upmu\)V\({}_{\text{RMS}}\) & 6.7 \(\upmu\)V\({}_{\text{RMS}}\) & 4.9 \(\upmu\)V\({}_{\text{RMS}}\) & 2.05 \(\upmu\)V\({}_{\text{RMS}}\) \\ noise & (1–108 Hz) & (1–100 Hz) & (0.5–100 Hz) & (1–130 Hz) & (0.1–10 kHz) \\ CMRR & \textgreater{}105 dB & 68 dB & 100–110 dB & 90 dB & \textgreater{}65 dB \\ NEF 2 & 4.28 & - & 37.3 & - & 2.26 \\ \hline \end{tabular}  
* Estimated gate oxide impedance, 2 NEF = Vni  
\end{table} 
Table 1: Performance summary and comparison.