Summary: Are power planes in a 4 layer PCB any good as a capacitor? Can it work as one big bypass capacitor? A look at an discussion on PCB layer stackups, and some measurements on 4 and 8 layer PCB power planes with different prepreg thicknesses and how well they work as a capacitor. https://www.xilinx.com/support/documentation/application_notes/xapp623.pdf https://www.researchgate.net/publication/242415439_High_Performance_FPGA_Bypass_Networks ...
