Lab #6
Follow the instruction and procedures in the Student Manual, unless specified differently
in this note.
Reading:
p.124 – 138 in SM
Ch. 2.15 – to end in AE
6-1 Use the following set-up for the differential amplifier shown below. (Both +Vin and
–Vin should be connected to the output of FG2 through 100 Ohm resistors). Estimate the
common mode gain and differential mode gain of the circuit. Use 3 Vp-p 100 Hz sine
wave to measure Gcm. Use .2 Vp-p 1 kHz for Gdm. Follow the instruction. What is the
CMRR for parts A & B?
6-2 Follow the instruction. Note that there is no direct connection between 10 k
resistors and 0.1 uF capacitor in the circuit.
6-3 Skip
6-4 Follow the instruction. It won’t be easy to pull Ic down to 1 mA range. If you
measure around 6 mA with 20 MOhm, you are OK. Conduct simulation as described
below and compare the results between your measurement and simulation.
6-5 Skip
step 3: Running parametric simulations
Step 1: Draw the circuit schematic
The parts need are: 2 Q2N3904 transistors 3
Resistors 2 Voltage supplies DC 3
connections to GrouND
BUBBLEs
• Use Ctrl-r to rotate and Ctrl-f to flip the parts
accordingly.
• Enter the parameter values for all known
parts and label the bubbles
Step 2: Set up parametric simulations
• Here, we will set up the program to calculate
currents and voltages in the above circuit for
different values of a PARAMETER (R3 in
this case). The value of this parameter will be
a name inside the curly brackets (i.e.
{AbCdE})
• In the part list search for PARAMETER
and place it on the schematic
• Double click on the PARAMETER. In the
name field type the parameter name without
the curly brackets
• For value, type the DC Bias Point value.
• Under “analysis”, choose “set up” and
select PARAMETRIC
• Click on parametric and enter the
following parameters:
Sweep var. Type: Global parameter
Name: R
Sweep Type: Linear
Start Value: 500
End Value: 5k
Increment: 0.5k
• Click “OK”
• Select TRANSIENT
• Close the “set up analysis” tab
• Run the simulation (“analysis”“simulate”). When you get the error “failed
to update….”. Just click ok and run again.
step 4: Markers and Output file
• The probe program produces an output file
(>View>Output File in the new window)
which contains all relevant information
about the circuit (i.e. device parameters,
Beta AC, Beta DC, Power dissipation, etc.)
• By pressing the V or I button on the
toolbar, the voltages and currents will be
displayed on the schematic (for the most
recent value of R3). By placing the current
or voltage markers anywhere you need on
the schematic, you will get the time
dependence of the voltage/current as a
function of time (useful later for ac circuits).