Download Experiment #3: Diode AND gate

Diode OR Gate
Modeling:
1. Design a diode OR gate in which the maximum input current, I in is less than 5mA.
a. Use two D1N4002 diodes.
b. Plot the voltage transfer function by varying the input voltage on Pin A from 0 V
to 5 V while holding the voltage at Pin B to 0V. Determine the diode voltage for
D2.
c. Verify that the maximum current is within specification when VA = 5 V and VB =
0V as well as when VA = VB = 5 V.
2. Simulate the circuit again after substituting two D1N914 diodes for the D1N4002 diodes.
a. Plot the voltage transfer function by varying the input voltage on Pin A while
holding the voltage at Pin B to 0V.
b. Determine the maximum input current.
3. Determine the differences between the diodes.
a. Click on D1N4002 in the PSpice simulation, causing the part to be highlighted in
red.
b. Select EDIT/MODEL
c. In the pop-up window that opens, select EDIT INSTANCE MODEL (Text).
d. Scroll through the parameter listed to find RS, the series resistance of the diode,
IS, the reverse saturation current, and VJ, the turn-on voltage (or Von) of the
diode.
e. Repeat these steps with D1N914 to determine RS, IS, and VJ for this diode.
Measurement:
4. Build one of the two circuits that you have simulated in the pre lab.
a. Measure the output voltage when VA = VB = 0 V, VA = 5 V and VB = 0V, VA = 0
V and VB = 5 V, and VA = VB = 5 V. Construct the function table for the circuit.
b. Using the arbitrary function generator, sweep the input voltage VA from 0 V - 5 V
while VB = 0 V. Plot the voltage transfer function using the X-Y plot capability.
Determine the magnitude of the output voltage when the input voltage VA is
equal to 0 V, 0.7 V, 1.4 V, 3 V, 4.3 V, and 5.0 V.
c. Measure the input current when the input voltage VA is 0 V, 0.7 V, 1.4 V, 3 V,
4.3 V, and 5.0 V. Compare the maximum value for the input current with that
obtained from your simulation.
d. Using a curve tracer and the digital multimeter, determine Von and R1. Use these
results to briefly explain the differences between your simulations and the
experimental results.
Variations on Experiment:
1. Instead of the D1N914, use two red LEDs. Use the values for Von, Rs, and Is calculated
in the Diode IV Characteristics experiment for VJ, RS, and IS, respectively.
2. Cascade two diode OR gates. Connect the arbitrary function generator to Pin A on the
first gate. Tie Pin B on the first gate and the unused input on the second gate to 0 V.
Measure the output voltage of the second OR gate as the voltage output from the arbitrary
function generator is ramped from 0 V to 5 V. Given that TTL logic levels are as
follows: A logical “0” is equal to a voltage between 0 V-0.7 V and a logical “1” is equal
to a voltage between 2 V – 5 V. What is the maximum number of diode OR gates that
can be cascaded together such that the output voltage is within the definition of a TTL
logical “0” and “1” when the input voltage on Pin A is either 0 V or 5 V.