1. The problem statement, all variables and given/known data Supposed to find Ro for a CS MOSFET amp given V'A=10V/μm, L=0.4μm, and ID=100μA. 2. Relevant equations Ro=ro=V'A*L/ID 3. The attempt at a solution I say that ro=10μ*0.4μ/100μ= 10*10^-6*0.4*10^-6/100*10^-6 = 4*10^-8 Book says "10x0.4/.1=40kΩ" .. what exactly went into that? for one thing (10*0.4)/.1 does not = 40,000. also if you multiply something in micrometers by something in micrometers, then divide by something in microamps, you should end up with a very small number, I think. I'm sure 40kΩ makes sense somehow but they're doing a bad job of explaining it.