# A High Performance 0.3 V Standard-Cell-Based OTA Suitable for Automatic Layout Flow
## 9 Conclusions  
In this paper, we have presented an improved standard-cell-based differential-to-single-ended converter and a novel standard-cell-based basic voltage amplifier. These building blocks have been exploited to implement a standard-cell-based ULV OTA with state-of-the-art performances. The layout of the OTA has been implemented by using a fully automated place-and-route flow by using the Cadence Innovus tool and starting from the Verilog netlist of the circuit. Simulation results have shown a dc gain of 50 dB with a gain-bandwidth product of 10 MHz with a 150 pF load capacitance. The \(THD\), simulated at a frequency of 100 Hz and with an amplitude equal to 80% of the rail-to-rail input swing, has ended up as low as 0.24%, showing very good linearity performance for a ULV standard-cell-based OTA. Compared to other ULV OTAs from the literature, the proposed OTA exhibits FOMs of about 128,000 \(\frac{\text{MHz-pf}}{\text{mW}}\), with an area footprint of only 598 \(\upmu\text{m}^{2}\), resulting in the best values for both \(FOM_{5}\) and \(FOM_{5,A}\). \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & \multicolumn{3}{c}{**Automatic Layout Flow Available**} & \multicolumn{3}{c}{**Automatic Layout Flow Not Available**} \\ \cline{2-9}  & **This Work \({}^{\ddagger}\)** & [33]\({}^{\ddagger}\) & [51]\({}^{\ddagger}\) & [39]\({}^{\ddagger}\) & [11]\({}^{\ddagger}\) & [12]\({}^{\ddagger}\) & [66]\({}^{\ddaggeragger}\) \\ \hline Year & 2023 & 2022 & 2022 & 2021 & 2022 & 2020 & 2018 \\ \hline Technology [\(\upmu\)m] & 0.13 & 0.13 & 0.13 & 0.18 & 0.13 & 0.18 & 0.18 \\ \hline \(V_{DD}\) [V] & 0.3 & 0.3 & 0.3 & 0.3 & 0.3 & 0.3 & 0.3 \\ \hline \(DC_{gain}\) [dB] & 50.33 & 34.97 & 28.3 & 30 & 52.92 & 64.7 & 65.8 \\ \hline \(C_{L}\) [pF] & 150 & 2 & 1.5 & 150 & 50 & 30 & 20 \\ \hline \(GBW\) [kHz] & 10.40 k & 12.69 k & 15.42 k & 0.25 & 35.16 & 2.96 & 2.96 \\ \hline \(m_{\varphi}\) [deg] & 56.33 & 62.56 & 54 & 90 & 52.40 & 52 & 61 \\ \hline \(SR_{p}\) [V/ms] & 631.4 & 4.54 k & 9.08 k & - & 18.61 & 1.9 & 6.44 \\ \hline \(SR_{n}\) [V/ms] & 811.3 & 6.82 k & 9.08 k & - & 11.51 & 6.4 & 7.8 \\ \hline \(SR_{avg}\) [V/ms] & 721.35 & 5.68 k & 9.08 k & 0.085 & 15.06 & 4.15 & 7.12 \\ \hline \(THD\) [\%] & 0.24 & 3.38 & 3 & 2 & 0.67 & 1 & 1 \\ \hline \% of input swing & 80 & 90 & 80 & 90 & 90 & 85 & 93.33 \\ \hline \(CMRR\) [dB] & 42.88 & 27.08 & 41.07 & 41 & 42.11 & 110 & 72 \\ \hline \(P_{D}\) [nW] & 12.09 k & 6.10 k & 4.41 k & 2.4 & 21.89 & 12.6 & 15.4 \\ \hline \(Mode\) & STD-CELL & STD-CELL & STD-CELL & DIGITAL & BD & BD & BD \\ \hline \(FOM_{5}\) [\(\frac{\text{MHz-pf}}{\text{mW}}\)] & **128.2 k** & 4.16 k & 5.25 k & 15.89 k & 80.29 k & 7.05 k & 3.61 k \\ \hline \(FOM_{L}\) [\(\frac{\text{V-pf}}{\text{mW}}\)] & 8.949 k & 1.86 k & 3.09 k & 5.40 k & **34.40 k** & 9.88 k & 9.25 k \\ \hline \(FOM_{\text{i-wc}}\) [\(\frac{\text{V-pf}}{\text{mW}}\)] & 7.833 k & 1.49 k & 3.09 k & - & **26.30 k** & 4.52 k & 8.36 k \\ \hline \(Area\) [\(\upmu\text{m}^{2}\)] & 598 & 217.85 & **164** & 982 & 5200 & 8500 & 8200 \\ \hline \(FOM_{S,A}\) [\(\frac{\text{MHz-pf}}{\text{mW-um}}\)] & **214.38** & 19.10 & 32.01 & 16.18 & 15.44 & 0.83 & 0.4 \\ \hline \(FOM_{L,A}\) [\(\frac{\text{V-pf}}{\text{mW-um}}\)] & 14.96 & 8.54 & **18.84** & 5.50 & 6.62 & 1.16 & 1.13 \\ \hline \(FOM_{L_{w,A}}\) [\(\frac{\text{V-pf}}{\text{mW-um}}\)] & 13.10 & 6.84 & **18.84** & - & 5.06 & 0.53 & 1.02 \\ \hline \end{tabular} \({}^{\ddagger}\) Simulated; \({}^{\ddagger}\) Measured; \({}^{\ddagger}\) The automatic layout flow of [39] is not allowed on all the standard-cell libraries.  
\end{table} 
Table 5: Comparison table. **Author Contributions:** Conceptualization, R.D.S., F.C. and G.S. ; methodology, R.D.S., F.C. and G.S. ; software, R.D.S. ; validation, R.D.S. ; formal analysis, R.D.S. ; investigation, R.D.S. and G.S. ; resources, G.S. ; data curation, R.D.S. ; writing--original draft preparation, R.D.S. ; writing--review and editing, F.C. and G.S. ; visualization, F.C. and G.S. ; supervision, G.S. ; project administration, G.S.