Semiconductor Fundamentals Unit 6 – Transistor Load Lines and Gain
Exercise 4 – Transistor Load Lines
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the dc load line for a
transistor circuit. You will verify your results with a multimeter.
DISCUSSION
- Collector current characteristic curves are graphs of collector current versus collector-emitter
voltage as a function of base current. - Since beta is almost constant in the transistor active region, a plot of collector current versus
collector-emitter voltage with a constant base current is a curve that increases very slightly. - Dc load lines intersect the Y-axis at the saturation point and the X-axis at the cutoff point.
- The Q-point or operating point is the point at which the load line intersects IB and is
determined by the dc bias conditions of the transistor circuit. - Transistor circuits used for small signal amplification are usually designed to have the Q-
point in the center of the load line. This gives an active region operating range for the applied
ac signal. - Load line determination will be effected with changes in collector voltage supply or the value
of the collector resistor.