The characteristics of a field-effect...

🔍 Key Concepts

• How a FET behaves when fully ON vs fully OFF in a switching power supply • Difference between resistive, inductive, and capacitive behavior in simple DC circuits • Typical leakage resistance (how much current sneaks through) of a FET in the OFF state compared to very large resistors or open switches

💭 Think About

• When a FET in a RADAR switching power supply is being used as a switch and is fully ON, what simple circuit element does it most closely resemble from the point of view of DC current flow? • When that same FET is fully OFF, should it allow significant current to pass, or should it behave more like an open circuit? What simple component (or approximate resistance value) best represents that? • Which options describe behaviors that would be undesirable or unrealistic in a high‑efficiency switching power supply (e.g., storing energy like an inductor or capacitor when you just want a clean ON/OFF switch)?

✅ Before You Answer

• Check which answer choice describes very low resistance in the ON state and very high resistance or open circuit in the OFF state. • Eliminate any choices where the OFF state would still allow noticeable current flow (too low a resistance) or store energy like an inductor/capacitor instead of simply blocking current. • Confirm that the described ON state behavior matches what is wanted for a switching power supply FET: minimal voltage drop and minimal power dissipation.

The characteristics of a field-effect transistor (FET) used in a modern RADAR switching power supply can be compared as follows:

"On" state compares to a bipolar transistor. "Off" state compares to a 1-Megohm resistor.

"On" state compares to a pure resistor. "Off" state compares to a mechanical relay .

"On" state compares to an low resistance inductor. "Off" state compares to a 10-Megohm resistor.

"On" state compares to a resistor. "Off" state compares to a capacitor.

🔍 Key Concepts

💭 Think About

✅ Before You Answer