Experiment #8 Common Emitter

Pick five resistors between 2K2 and 1M for Rb. You want a range of resistors that allow you to see Vce when the trnsistor is the saturated switch region and when it is in the active amplifier region. I used 47K, 220k, 330k and 1M, but this can vary depending on your transistor. Some may need to use 2k2. Put one resisitor in place, and measure and record voltage drop across Vce and Vbe. Also measure and record the current for Ic and Ib. Then change the Rb resistor and do all the measurements and record the new readings. Do this for each of the resistor values above.

Rb: 2K2
Vbe: .778V
Vce: 26.5mV
Ib: 1.94mA
Ic: 6.19mA

Rb: 10KR
Vbe: .738V
Vce: 45.5mV
Ib: 0.42mA
Ic: 6.15mA

Rb: 47KR
Vbe: .709V
Vce: 90.5mV
Ib: 90uA
Ic: 6.06mA

Rb: 220KR
Vbe: .684V
Vce: .525V
Ib: 19.4uA
Ic: 5.29mA

Rb: 270KR
Vbe: .678V
Vce: .921V
Ib: 16.4uA
Ic: 4.49mA

Discuss what happened for Vce during this experiment. What change took place, and what caused the change?
: As resistance is increased the voltage for Vce increases.

Discuss what happened for Vbe during this experiment. What change took place if any, and what caused this change?
: Because the transistor is fully on with each resistor Vbe will be close to or around 0.7V as was shown by the results.

Discuss what happened for Ib during this experiment. What change took place, and what caused the change?
: As resistance increases Ib gradually gets smaller and smaller to the point where it gets into uA's.

Discuss what happened for Ic during this experiment. What change took place, and what caused the change?
: As with Ib, the more resistance that is added to the circuit the less current that will be sent to the collector.