Krdytkyu

up vote 2 down vote favorite I am failing to understand the purpose of the MOSFET in this circuit from Adafruit Feather board. The FET is connected with source and drain reversed comparing to typical high-side pMOS switch, so this is not a power switch. The combination of body diode with schottky should work like usual battery switch-over circuit, in which case what is FET doing there other than providing body diode? My only guess is that it is there to avoid voltage drop on the diode when battery supplies power. If source is at drain voltage (via body diode) and gate is pulled to ground (via R12) then MOSFET should be fully open. power mosfet share | improve this question ...

up vote 4 down vote favorite 3 I found a pattern that I want to prove: $$f(x) = 2^{lceil log_2(3^x)rceil} - 3^xquad {xinmathbb{Z}^+} $$ $$ lim_{xrightarrowinfty} f(x) = infty $$ Discussion: $$ f(x) = 2^{lceil log_2(3^x)rceil} - 3^x = 3^x(2^{lceil log_2(3^x)rceil-log_2(3^x)}-1)$$ $$0<lceil log_2(3^x)rceil-log_2(3^x)<1 Rightarrow 0<f(x)<3^x$$ $f(x)$ 's lower bound is zero and its upper bound tends to infinity. As far as I know, $f(x)$ can oscillate anywhere in between. However, after checking a few first thousands values of $f$ , I am convinced that the function indeed tends to infinity. I guess the fact that $x$ is an integer plays a role in that. If $lceil log_2(3^x) rceil$ was really close to $log_2(3^x)$ , $f(x)$ would be really close to $0$ , so the limit would not hold. Experimental result...