Open-Loop Phase (°) -360 -315 -270 -225 -180 -135 -90 -45 30 20 10 -10 -20 -30 20 -20 (a) (b) FIGURE 2: Welcome to Mt. Nichols. (a) A 3D version and (b) 2D topographic version. The orange line shows a typical third-order loop with approximately 6 dB of peaking when the loop is closed. The dashed white lines on (a) indicate the 0dB magnitude and -180 ° phase planes. MORE ON NORMALIZATION That sounds bad. I didn't mean " moron normalization. " What I meant was, there is even more to this powerful concept of normalization than is immediately apparent. In " There is Only One Loop, " it was argued that all feedback loops can be analyzed as unity-gain configurations, making the Nichols chart universal. But there's more. Consider the two Bode plots in Figure S2(a). These two loop transmissions have very different frequency responses, but as you can see in Figure S2(b), they look exactly the same on a Nichols chart and have the same relative stability! Whoa. 100 50 -50 -100 -45 -90 -135 -180 100 105 Frequency (rad/s) (a) 1010 (b) FIGURE S2: Frequency-agnostic properties of the Nichols chart. (a) Two very different Bode plots map to (b) the same trace in Nichols space. 40 0 dB 0.5 dB 0.25 dB 1 dB 6 dB 3 dB -1 dB -3 dB -6 dB -12 dB -20 dB 60 50 40 30 20 10 -10 -20 -30 It probably isn't accurate to refer to this frequency-agnostic behavior as normalization because frequency doesn't appear anywhere on the Nichols chart. It might be better to say that the Nichols space somehow strips off frequency information, leaving only the relationship between the poles and zeros of the loop transmission. But like normalization, it allows wildly diverse systems to be analyzed on one universal plot. Concepts this deep may require a yoga mat. -180 -135 Open-Loop Phase (°) -90 -45 80 60 40 20 -20 -40 IEEE SOLID-STATE CIRCUITS MAGAZINE SPRING 2022 21 Open-Loop Phase (°) Open-Loop Gain (dB) Closed-Loop Gain (dB) Open-Loop Gain (dB) Open-Loop Gain (dB) -360 -270 -180 -90 Open-Loop Gain (dB) Open-Loop Phase (°)