Bipolar transistors
When the output characteristics (IC-VCE) of a common-emitter transistor are plotted with base current IB as a parameter, what is characteristic of the active region?
- AEvery curve is a straight line through the origin
- BFor each IB, there is a nearly horizontal line that depends little on VCE
- CIncreasing IB decreases IC
Show answer and explanation
Answer: B. For each IB, there is a nearly horizontal line that depends little on VCE
In the active region, the collector current is set mainly by the base current and depends little on VCE. The output characteristics therefore look like a set of nearly horizontal lines, one for each IB, with spacing corresponding to hFE. The slight upward slope is due to the Early effect.
- A. The steep part near the origin is the saturation region; in the active region the lines are nearly horizontal.
- B. Correct. Lines of nearly constant IC, set by IB, are lined up.
- C. Increasing IB increases IC.