In a BJT, saturation occurs when Vce is too low, causing Ic to be limited and the output to clip.

• A. Vce is too high for conduction.
• B. Ib is zero.
• C. Vce is too low, causing Ic to be limited and output to clip.
• D. Temperature increases significantly.

Answer: (C)

Saturation in a BJT happens when both junctions are forward biased, so the collector-emitter voltage drops to a very small value. In this state, the transistor can’t pull the collector current higher just by increasing the base current because the current is now limited by the external circuit (the load and supply), not by the transistor’s ability to amplify. As a result, the output cannot swing much further toward the low rail and ends up clipped near Vce(sat), typically around a few hundred millivolts for silicon devices.

That’s why saying Vce is too low leads to Ic being limited and the output clipping matches the real behavior of saturation. Conversely, a high Vce puts the transistor in the active region where it can continue to conduct more Ic as Ib is increased; Ib being zero means the transistor is off with essentially no Ic; and while temperature can affect device parameters, it doesn’t define the saturated state.