MOSFET LED strip switching - wrong 1 PUBLIC

An INCORRECT application of an IRF540 MOSFET to switch a 12V SMD5050 LED strip load.

Example written for this stackexchange question, showing an incorrect application of a IRF540 MOSFET to switch a 12V load.

The problem here is that the gate is driven V_G at the supply voltage which is also supplied directly to the drain V_D. So the source voltage V_S when the MOSFET is on is close to the gate voltage and V_GS is nowhere near the full-on voltage needed to achieve its specified R_DS(on).

This MOSFET has a test R_DS(on) of 0.077Ω at V_GS 10V but this circuit delivers a V_GS of only about 4V.

Plot P(M_Load), V(M_G) - V(M_S) and I(M_Load.nS) in DC Solver to see what I mean. The solver reports a 3.6V V_GS and a P_{M_Load} of ~ 1.8W @ an I_DS of 500mA. I measure a much lower DS voltage drop in my real circuit and I haven't tried to measure dissipation, but it's in vaguely the right territory.

Corrected version can be found here.