N+ Collar Input Contact y Isolation x Input Contact N+ Emitter EPI P Type (NPN Base/LPNP Collector) P Type Injector z x y LPNP Emitter Input Contact LPNP Emitter P Isolation N EPI " Deep N " Collar N EPI NPN Base LPNP Collector FIGURE 6: The layout and cross section of the circuit inside the dashed box in Figure 5(a). The metal layer is not shown. EPI refers to the N-doped epitaxial layer grown on top of the P substrate. LPNP: lateral PNP. makes this whole thing work is not really our friend. It's actually pretty flat on the top, right where we need it most. As you try to increase the ADC resolution, the NPNs get closer and closer together, and the base voltage difference between them gets small very quickly. Since the base voltage from emitter to emitter is small, the amplitude of the differential output drops. This is particularly evident in the LSB output because the LSB has the most transitions and, hence, very little voltage between emitter locations. This is all painfully clear in Figure 10. The peak differential output voltage is plotted as a function number of emitters in the LSB. While it looks like there might be hope for 5 b, this plot is calculated for the peak FIGURE 8: The full discrete element schematic of the 4-b wiggler. All of the elements within the dashed line are included in the layout of Figure 7. (This LTSpice schematic is available at https://github.com/CMangelsdorf/SSCM.) IEEE SOLID-STATE CIRCUITS MAGAZINE SUMMER 2022 21 FIGURE 7: The full layout of the 4-b wiggler core showing the metal layer. NPN Emitter Buried Layerhttps://www.github.com/CMangelsdorf/SSCM