# NPN Transistor Output characteristics (CE)

The basic working principle of a transistor is controlling a bigger current in circuit using a small current in another circuit. Being a three terminal device, one terminal has to be common for the two crcuits. The common emitter configuration is very common in most of the applications. We can explore the working of the transistor by studying the relationships between various voltages at different terminals and currents through them.

# Objective

Using an NPN transistor, plot the Collector voltage against the collector current in a common emitter configuration. Repeat it for different base currents. Collector current is calculated from the voltage across the a 1kΩ resistor, in the collector circuit.

# Procedure

- Fix the transistor on a bread board and make the connections.
- Set base voltage to 1 volt and press the START button.
- Repeat for different base currents, increment PV2 by 0.3 volt steps.

The resulting graphs are shown below. This experiments also can be done manually from the oscilloscope GUI, by noting down the readings.

# Discussion

The characteristic curves for different base currents are shown in figure. The collector current is obtained from the voltage difference across the 1kΩ resistor.

The base current is set by setting the voltage at one end of the 100kΩ resistor, the other end is connected to the transistor base. The value of base current is calculated by, Ib= (VPV2VA2) ⁄ (100 × 103) × 106μ A. If A2 is not connected, the code assumes 0.6 volts at the base to calculate the base current.