Meaning with no signal the mosfet gate is grounded and there's no load. But as you feed it signal from the function generator, that brings the gate up and turns the mosfet on loading the supply. And if you make
MOSFET temperature sensors of on-chip thermal testing. Sens. Act. A Phys. 2013, 203, 234–240. [CrossRef] 46. Olsson, R.H.; Buhl, D.L.; Sirota, A.M.; Buzsaki, G.; Wise, K.D. Band-tunable and multiplexed integrated circuits for simultaneous recording and stimulation with ...