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Experiment #13: Bipolar Transistors and Amplifiers
Performed on 5/1/2015
Joe O’Connor | Onochie Ani
This experiment had us use the NPN bipolar junction transistor. We used that transistor and measured
current and voltage of the transistor using the DMM and an oscilloscope. We also learned how to bias the
transistor and have it act as an amplifier in a circuit. Overall this experiment has 21 steps.
Step 1:
This first step required us to setup the circuit like figure 3 using the 2N2222 transistor. We then used the
triple output power supply and had that be PS1. Then PS2 was the single output power supply. We then set max
current to be 200mA.
Using the data sheets we determined that hfe max should be 300 and the min should be 100.
Step 2:
To begin this step we turned PS2 off and then adjusted PS1 so that ib = 15uA. We them measured ic as vCE
(PS2) increased from 0 to 1V in 0.1V steps and from 1 to 10V in 1V steps. Our values are below. We saw that ic
increases very fast then it slowly increased after 0.3V.
Steps 3-4:
These steps had us repeat step 2 but for iB set at 35. The values we got are in the table and chart on the
next page:
vCE
iB
iC
B
vCE
iB
iC
B
1
0.00832
0.00239
3.8
12
0.000141
0
0.3
2
0.00588
0.00235
4.3
10
0.00087
0.000627
0.8
3
0.00589
0.00233
4.9
0.3
0.00476
0.002278
1.4
4
0.00589
0.00231
5.4
0.4
0.00654
0.00228
1.5
5
0.00643
0.00235
5.9
6
0.5
0.00564
0.002296
1.7
6
0.00653
0.00232
6.2
4
0.6
0.00576
0.00231
1.9
7
0.00686
0.002484
6.5
iB
0.7
0.00596
0.00232
2.3
8
0.00697
0.002498
6.8
2
iC
0.8
0.00565
0.00239
2.5
9
0.00697
0.00245
7.5
0
0
0.00001
0.1
0.0004
0.2
0.9
0.00587
0.00239
2.8
10
0.00697
0.00246
8.2
iB
iC
8
B
vCE
B
0
0
We noticed that B increased as ic increased.
0.5
1
Steps 5-6:
For these steps we had to hook up the 2N2222 transistor to mimic figure 4 below:
Then we set PS1 to 0V and PS2 (Vcc) to 9v. We then measured th actual values of our resistors. R100 was
104.3k ohms and R1 was 0.994 k ohms. Then we used the DMM to measure the input/output of the circuit. We
predicted the plot to look like figure 6.33 in the book.
Steps 7-9:
These steps we had to build the circuit shown in figure 4. We were told to keep the connections short as
possible to avoid getting noise and also we had to use a single ground point. We then varied PS2 from 0 to 9V in
250mV steps while Vcc was set to 9v. The results we got are in the table below:
vBE
vCE
vBE
vCE
vBE
vCE
vBE
vCE
vCE
0.00178
9
0.676
6.38
0.693
2.996
0.698
0.256
0.354
9
0.678
6.09
0.695
2.548
0.699
0.203
10
0.547
8.798
0.679
5.689
0.697
2.256
0.699
0.201
8
0.608
8.799
0.681
5.265
0.699
1.786
0.699
0.195
0.645
8.425
0.683
4.857
0.699
1.654
0.699
0.19
0.668
8.025
0.689
4.492
0.699
1.126
0.7
0.182
0.669
7.58
0.69
4.018
0.698
0.798
0.7
0.181
0.67
7.17
0.691
3.906
0.697
0.546
0.7
0.18
0.672
6.79
0.692
3.348
0.698
0.352
0.714
0.175
0.716
0.162
6
vCE
4
2
0
0
0.5
1
Steps 10-11:
For these steps we had to build the circuit of figure 5 using a 6.8uF capacitor on the base. We omitted the
100nF and RL. We then adjusted PS1 to set Vce to be around 5VDC. Then we checked the Vce to make sure it was
unchanged from step 9 and that was true.
Steps 12-13:
We began these steps by setting the FG for a high Z output, 1kHz sine wave with 15 mV peak (30mVp-p).
Using figure 5 we tested the circuit without the 100nF capacitor and RL. We used channel 1 of the oscilloscope to
monitor be and channel 2 to monitor Vout. Our waveforms are below:
Steps 14-16:
For these steps we had to analyze the sinusoidal waveform from the step above. From the scopes cursors
we can calculate the amps measured voltage gain by the formula Av=Vout(pk-pk)/Vin(pk-pk)
Step 17:
For this step we slowly increased the amplitude of Vin until out starts to clip (visibly distorted). We got the
max value of vout to be 2V and the min to be -7V. We determined that vout flattened because the circuit holding a
charge due to the resistances.
Step 18:
For the last step, we had to repeate step 11 to and set Vce to 6VDC and then repeated steps 12-17 again
for this particular setup. We set PS1 so that Vce would be about 6VDC. When we slowly increased Vin and Vout
until we saw distortion we got Vout max to be 3V and the min to be -6V.