# Energy-Efficient Amplifiers Based on Quasi-Floating Gate Techniques
## 5 Discussion  
A summary of the main performance parameters of the amplifier is shown in Table 1, including parameters from other reported amplifiers for comparison. Since the fabricated  
Figure 11: Measured total harmonic distortion (THD) versus input amplitude.  
Figure 12: Measured frequency response of the proposed amplifier connected as voltage follower.  
Figure 10: Measured transient response to a square input signal.  
amplifier is in unity-gain closed loop, open-loop performance parameters (DC gain, Phase Margin PM, Common-Mode Rejection Ratio CMRR and Power Supply Rejection Ratio PSRR) were obtained from post-layout simulations using BSIM4 MOSFET models and the Spectre simulator available in Cadence IC6.1.  
Note that the proposed amplifier showed improved small-signal and large-signal performance just drawing 30 \(\upmu\)A from the \(\pm\)0.5 V power supply. A graphical comparison of FoM\({}_{\text{L}}\) and FoM\({}_{\text{S}}\) with different reported amplifiers is shown in Figure 13, where the advantages of the proposed approach are evidenced. Note the good balance between both figures of merit, as deduced from their average value (FoM\({}_{\text{AVG}}\)) in Table 1. The main drawback of the proposed amplifier is the extra silicon area required for the capacitors C\({}_{\text{BAT}}\), employed for dynamic cascode biasing, as can be seen in Figure 8b.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Parameter (units)** & **Figure 8** & **[**18**]** & **[**19**]** & **[**69**]** & **[**70**]** & **[**72**]** & **[**73**]** & **[**74**]** & **[**75**]** & **[**76**]** \\ \hline CMOS process (nm) & 130 & 180 & 500 & 500 & 500 & 40 & 180 & 180 & 130 \\ Supply voltage (V) & \(\pm\)0.5 & \(\pm\)0.9 & \(\pm\)1 & \(\pm\)1 & \(\pm\)1 & 1.1 & 0.8 & 0.7 & 1.8 & 1.2 \\ Capacitive load (pF) & 140/120 & 23 & 70 & 80 & 70 & 0.5 & 8 & 20 & 200 & 5.2 \\ SR+ (V/\(\upmu\)s) & 5.7 & 24.11 & 9.8 & 100 & 13.2 & 1250 & 0.14 & 1.8 & 74.1 & 98.7 \\ SR- (V/\(\upmu\)s) & \(-\)7.1 & \(-\)23.33 & \(-\)7.6 & \(-\)78 & \(-\)25.3 & – & – & \(-\)3.8 & – & – \\ DC gain (dB) & 63.88 a  & 67 & 81.7 & 43 & 76.8 & 49 & 51 & 57.5 & 72 & 75.4 \\ PM (c) & 61 a  & 84 & 60 & 89.5 & 75.1 & 65 & 60 & 60 & 50 & 82.5 \\ GBW (MHz) & 4.48 & 0.57 & 4.75 & 0.725 & 3.4 & 3600 & 57 & 3 & 86.5 & 166.1 \\ CMRR @DC (dB) & 56.7 a  & 73.2 & 78 & 68 & 112 & – & – & 19 & – & – \\ PSRR+ @DC (dB) & 61.5 a  & 44.1 & 72 & 55 & 92 & – & – & 52.1 & – & – \\ PSRR- @DC (dB) & 71.9 a  & 41.8 & 74 & 58 & 113 & – & – & 66.4 & – & – \\ Eq. input noise @1 MHz & 27.5 & – & 35 & 230 & 23 & – & – & 100 & – & – \\ (nV/\(\upmu\)Hz) & 30 & 14.5 & 120 & 120 & 100 & 3300 & 1.2 & 25.4 & 11900 & 236.4 \\ Power (\(\upmu\)W) & 0.009 & 0.030 & 0.024 & 0.024 & 0.030 & 0.050 & 0.057 & 0.020 & 0.070 & – \\ FoM\({}_{\text{L}}\) (\(\upmu\)A/\(\upmu\)A) & 29.90 & 67.72 & 10.15 & 118.67 & 26.95 & 0.21 & 0.75 & 1.54 & 2.24 & 2.61 \\ FoM\({}_{\text{S}}\) (MHz:pF/mA) & 17920 & 1627.4 & 5541.7 & 966.7 & 4760 & 600 & 304 & 1653.5 & 2616.8 & 4384.4 \\ \(FOM_{AVG}=\) & 732 & 332 & 237.1 & 338.7 & 358.1 & 11.18 & 15.1 & 50.5 & 76.6 & 106.9 \\ \(\sqrt{FOM_{S}FOM_{L}}\) & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary of measurement results and performance comparison.  
Figure 13: Performance comparison.