17-04-2012, 11:46 AM
Logic Gates Digital Integrated Circuits
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Theory
I’ve used the schematic of a quad NAND gate as a representation to the
kind of IC that I have used in the experiment which includes 7408 and 7432
corresponding to AND,and OR respectively. The NOT gate IC (7404) is
different in that it has 6 NOT gates in it.
Digital logic circuitry does not make use of split power supplies as opamps
do. Like op-amp circuits, though, ground is still the implicit point
of reference for all voltage measurements.
Procedure and Results
We get to familiarize with the circuit even though a thorough familiarization
with the actual circuit inside the IC is not so easy. The basic circuit
for all the gates is the same. We supply a power supply though the pins
and 14 of the IC where the positive lead from the DC voltage supply goes
to 14 and pin 7 is grounded(effectively connected to the negative terminal).
As we can see in the above schematic diagram, we connect the the
schematic input leads of the gates (i.e. like pins 1 and 2) to the ground line
via switches. Now, by varying the switch position we can get an output
from the pin 3 which can be measured using a DMM.
AND Gate combines with OR Gate
We have two possible combinations where in one case we take the output
from the AND gate and give it as one of the inputs for the OR gate and the
vice-versa. Here, we have three switches in total; two in the first gate and
combination of NOT and OR gates
Similar to the above case, here also we have 2 possibilities i.e. NOT(OR)
and OR(NOT) where NOT(OR) is also known as the NOR gate. Here,there
are only two swiches as there is only one input to a NOT gate.
one in the second gate. Let’s look at both of them.