Module 3 Lab: Determining Beta for BJTs Wire the circuit  shown, with Rc = 470 Ω  and Q =  2N3904 · Record Ib and Ic  in the table below for the given values of RB RB Ib Ic Vbe Vce Beta 1MΩ 470KΩ 200KΩ 100KΩ 47KΩ · Return the RB value to 470KΩ, (A) Squeeze the transistor between your fingers to raise the case temperature, record any change in collector current  _______ (B)  Put a piece of ice in a plastic bag and hold it on the transistor to reduce the case temperature, record any change in collector current __________ · Describe your perception of  the relationship between Beta and case temperature. · Describe the behavior of Beta vs Ic Written Assignment 4 Answer all of the following questions/problems and submit them to your mentor.   Questions: 1. In a transistor circuit, the two extreme ends of the loadline are called: 2. When used as an amplifier, the transistor is usually biased in the region called the _______________ region. 0. The Q  point for an amplifier  is identified as _______ & _______ , which together determine the power dissipated  in the transistor. Problems: 1. For the circuit shown,  VBB = +10v,  Vcc = +30v, RB = 470kΩ, Rc = 6kΩ  Calculate the operating point for the circuit shown for a Beta value of 90 and for a Beta value of 130. 2. For the circuit shown,  Vcc = -10v, R1 = 10kΩ,  R2 = 2.2kΩ,   Rc = 3.6kΩ, RE = 1kΩ.  Calculate the operating point for the circuit shown.  Use IB = IC / Beta and calculate IB for Beta = 90. Module 4 Lab: AC Riding on DC R1 = 2.2KΩ    R2 = 4.7KΩ   C = 0.1uF   Vdc =  +5v  Vac = 3v peak  f = 1KHz · Use superposition to calculate the  DC  voltage at  point X     VDC =  ______ · Use superposition to calculate the  AC  (peak)  voltage at  point X     VAC =  ______ · Sketch what you think the scope will show at X: · Wire the circuit and connect a scope probe at X, be sure to DC couple the input and set the ground level at the bottom of the scope display, then sketch the results. Written Assignment 5 Answer all of the following questions/problems and submit them to your mentor.   Questions: 1. Describe what is meant by the voltage gain of an amplifier. 0. What is the primary purpose of coupling capacitors in transistor amplifiers? Problems: 1. If  the input voltage to an amplifier is  50mV and the resulting output voltage is 3V, calculate the voltage gain. 0. A transistor is biased with  IE = 5mA.     Calculate r’e 0. For the circuit shown, calculate:   a. The input resistance at the base of the transistor. a. The input resistance of the amplifier. a. The voltage gain. 0. If a circuit requires a capacitor to give  good coupling at 200Hz and the resistance the capacitor is connected to is  3Kohms,  what value capacitor is needed? Module 5 Lab: Amplifier Gain and Comparing Constant Bias to VDB Part I (A) Wire the circuit shown. [ you will determine the β value from DC measurements] R1 =   ...

1. Module 3 Lab: Determining Beta for BJTs
Wire the circuit shown, with Rc = 470 Ω and Q = 2N3904
· Record Ib and Ic in the table below for the given values of RB
RB
Ib
Ic
Vbe
Vce
Beta
1MΩ
470KΩ
200KΩ
100KΩ

2. 47KΩ
· Return the RB value to 470KΩ,
(A) Squeeze the transistor between your fingers to raise the case
temperature, record any change in collector current _______
(B) Put a piece of ice in a plastic bag and hold it on the
transistor to reduce the case temperature, record any change in
collector current __________
· Describe your perception of the relationship between Beta
and case temperature.
· Describe the behavior of Beta vs Ic
Written Assignment 4
Answer all of the following questions/problems and submit
them to your mentor.
Questions:
1. In a transistor circuit, the two extreme ends of the loadline
are called:
2. When used as an amplifier, the transistor is usually biased in
the region called the _______________ region.
0. The Q point for an amplifier is identified as _______ &
_______ , which together determine the power dissipated in the

3. transistor.
Problems:
1. For the circuit shown, VBB = +10v, Vcc = +30v, RB =
470kΩ, Rc = 6kΩ Calculate the operating point for the circuit
shown for a Beta value of 90 and for a Beta value of 130.
2. For the circuit shown, Vcc = -10v, R1 = 10kΩ, R2 = 2.2kΩ,
Rc = 3.6kΩ, RE = 1kΩ. Calculate the operating point for the
circuit shown. Use IB = IC / Beta and calculate IB for Beta =
90.

4. Module 4 Lab: AC Riding on DC
R1 = 2.2KΩ R2 = 4.7KΩ C = 0.1uF Vdc = +5v Vac = 3v
peak f = 1KHz
· Use superposition to calculate the DC voltage at point X
VDC = ______
· Use superposition to calculate the AC (peak) voltage at
point X VAC = ______
· Sketch what you think the scope will show at X:
· Wire the circuit and connect a scope probe at X, be sure to DC
couple the input and set the ground level at the bottom of the
scope display, then sketch the results.

5. Written Assignment 5
Answer all of the following questions/problems and submit
them to your mentor.
Questions:
1. Describe what is meant by the voltage gain of an amplifier.
0. What is the primary purpose of coupling capacitors in
transistor amplifiers?
Problems:
1. If the input voltage to an amplifier is 50mV and the
resulting output voltage is 3V, calculate the voltage gain.
0. A transistor is biased with IE = 5mA. Calculate r’e
0. For the circuit shown, calculate:
a. The input resistance at the base of the transistor.
a. The input resistance of the amplifier.
a. The voltage gain.
0. If a circuit requires a capacitor to give good coupling at
200Hz and the resistance the capacitor is connected to is
3Kohms, what value capacitor is needed?

6. Module 5 Lab: Amplifier Gain and Comparing Constant Bias to
VDB
Part I
(A) Wire the circuit shown. [ you will determine the β value
from DC measurements]
R1 = 20KΩ, R2 = 5MΩ ( two 10MΩ in parallel ), R3 =
20KΩ, C = 0.1uF, use 2N3904 for the transistor
· Measure D.C. Vc = _____ and Vbe = _____
· Calculate Ic = ( Vcc - Vc )/ Rc = ______ and IB = ( Vcc -
Vbe )/ RB = _____ then β = _____
(a) Verify that Rbe = Rin base = β re’
· Measure A.C. voltages vc = ____ vbe = _____
· Calculate ib = ( 10mV – vbe ) / 20 Kohms = _____
· Calculate ic = vc / 20kΩ = _____ calculate βac = ic / ib =
______
· Rbe = vbe / ib = _____ re’ = 25mV/ IE = _______ ic =
βac ib = ____
· Also calculate Rbe = βac re’ = _____ does this check with
the value above?

7. (B) To show the effects of changing beta on the Q point.
· Hold your finger on the case to raise the temperature and the
Q point should change (Vc goes down) due to the fact that beta
goes up as temperature goes up causing an increase in Ic.
· With a piece of ice in plastic bag, hold it on the transistor to
cool it; this should cause beta to decrease. The Q point will
change again ( Vc goes up ).
Part II
To show the advantage of VDB over CCB
· Wire the VDB circuit shown. The transistor beta value was
determined in part A.
· Measure [ D.C.] VB = ____ and VE = _____
· Calculate IE = _____ and re’ = _____
· Measure [ A.C. ] vin = _____ and vo = ____
· Now calculate voltage gain by two methods:
. Av = vc / vin = ______ and Av = Rc / re’ = _______.
. Do these two values match?
· Next hold your finger on the transistor and notice that the Q
point does not change. Change the transistor and again note
that the Q point stays constant.
Written Assignment 6
Answer all of the following questions/problems and submit
them to your mentor.

8. Questions:
1. For each circuit shown, indicate if it is CE, CB or CC
amplifier.
Figure A
Figure B
Figure C
0. Show two transistors connected as a Darlington amplifier. If
one transistor has a beta of 25 and the other has a beta of 60,
calculate the beta value of this combination.
Problems:
1. For the amplifier shown, if beta = 150
(a) Calculate the input impedance at the base
(b) Calculate the input impedance of the stage.
0. Shown here is a frequency response curve for an amplifier.
ESTIMATE the following:
(a) What is the high cutoff frequency ?
(b) What is the low cutoff frequency?
(c) What is the bandwidth?
0. An amplifier has a gain of 500, what is the dB gain?
0. A three stage amplifier system has dB gains of 15dB, 32dB
and 6db. What is the overall gain of the system in dB?

9. Module 6 Lab: Class A BroadBand Amplifier
Wire the circuit shown:
R1 = 68KΩ, R2 = 10KΩ, R3 = 10KΩ, R4 = 200Ω ( two 100Ω
in series ) , R5 = 2.2KΩ, C1 = 0.1uF, C2 = 0.1 uF Q1 =
2N3904
· Set the sig. Gen to 50mv RMS. With frequency equal to
10KHz.
· Record vo for the frequencies listed.
vo
f ( KHz) 10KHz 25 KHz 50 KHz 100 KHz 500 KHz
1MHz 2 MHz 3MHz
Calc Av
· Plot Av versus frequency on semi log paper.