Lab #4
Follow the instruction and procedures in the Student Manual, unless specified differently
in this note.
Reading:
p.82 – 99 in SM
p.61 – 79 in AE
Lab #4
4-1 Follow the instruction. Ignore the last sentence “You can even distinguish….” You
will find that is not the case. Don’t be surprised to see larger BC junction than BE.
4-2 Follow the instruction. Instead of using +15V and –15V as indicated by the circuit
diagram, use +12V and –12V from the power supply on the protoboard (we will use
12V to power transistors from now on).
4-3 Follow the instruction. You will have to estimate two β values, one from Zin
measurement and the other from Zout measurement (lens effect).
4-4 Follow the instruction, but use Vcc from the protoboard power supply (12V instead of
15V). You should have little trouble seeing clipping from the (-) side. Is there any
clipping for the (+) side? At the maximum amplitude, measure the base voltage with
the oscilloscope. What happens the quiescent level at base? In answering the fine
point, consider what would happen if Vb > Vc. Consider the base-collector junction
as another p-n junction. The base will start to see collector (meaning current will
flow to collector).
4-5 Follow the instruction. You will measure β directly in this experiment. In addition to
the 5 values listed in the manual, also measure with 10k, and 4.7k. Identify the region
where you have almost constant β values.
4-6 Follow the instruction. You can use the resistor box instead of the 10K variable
resistor, but choose values (<10K) that allows you to see a constant current. Take at
least 4 to 5 data points for R < 1K. Plot I vs R and identify the region of a good Isource. At what load resistance do you observe the drop in current? Compare the
observed value to calculations. Voltage compliance is the lowest collector voltage
where the transistor works as a good I-source.
4-7 Follow the instruction. Don’t forget to put your OSC in DC coupled mode to see the
quiescent point. Does it form a low pass filter or high pass filter? What R and C
form the filter? When you measure the output impedance, why do you have to use a
blocking capacitor? Use about 5 kOhm resistor to measure Zout.
4-8 Do this part. It is not optional.
4-9 Skip this part.