Logic Gates IC Chips

[felto]

Hi all
I would like to know how to test the logic gates of an IC chip, for instance a 'NAND' gate or an 'AND' gate in a circuit with my voltmeter. I do not have an oscilloscope but my voltmeter is capable of reading the highs and lows of the logic gates. Where do I need to hook up the leads from the voltmeter? Let us use the 74LS00 IC chip (Quad-input 'NAND' gate) as an example. see the picture attached. Any help can be greatly appreciated.

[MP]

You will need a voltage source. Use the voltage source to set the gate pins high and a ground to set the pins low. Use this procedure to test the logic table associated with the chip.

MP

[felto]

sorry but I dont follow you exactly.
I have to remove the chip from the board?
or can I just plug the board in and use
that source? How do I establish the highs
and lows? How do I know when one input
is high and the other is low or both? can you
tell me exaclty how to wire it up. Thanks for your help.

P.S. I prefer not to remove the chip from the board
because the board contains many chips and I dont
know which one is bad.

[MP]

connect +5 VDC to Vcc and connect Ground to -Vcc. Use ground as a logic 0 and use +5 VDC as a logic 1. Test the following truth table for each gate of the NAND gate 74LS00:
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
The inputs A and B are the two lines going into the gate (does not matter which is marked as which) and Y is the output from each gate.

The truth table for the AND gate is different.

MP

[felto]

So what your saying is just hook up the 5 volts to the chip
and I would see a 1 and 0 at the input then with my voltmeter
I would see a 1? Where would I hook up the voltmeter? positive to the output and negative lead to ground?

[Guest Alun]

So what your saying is just hook up the 5 volts to the chip
and I would see a 1 and 0 at the input then with my voltmeter
I would see a 1? Where would I hook up the voltmeter? positive to the output and negative lead to ground?

Yes, just connect the poisitive of meter to the ouput and the negative to 0V.

[felto]

Thanks for your help

How would you test an OPAMP?
for ex. the LM324

[Kevin Weddle]

To test the opamp I would just adjust the offset and determine that it switches in polarity. In the case where you don't have an offset null, you will have to apply direct voltage. Don't worry about the values, just check to make sure the polarity of the output reflects the input.

[felto]

Thanks Kevin.

Hey Kevin how would you test an 'AND' gate chip
with a voltmeter?

[lisa08]

??? what does a half and full adder do??

[ECET0purdue]

new logic chips are cheep probly easier to buy new ones and replace the old ones... unless you live in indiana.

[MP]

Thanks Kevin.

Hey Kevin how would you test an 'AND' gate chip
with a voltmeter?

This would be the same as my description above for a NAND gate, except the logic table is different. When you see a logic zero, the voltage is 0. When you see a logic 1, the voltage is full scale. In the case of my example above, a logic 1 would be 5 volts.

MP

[steven]

hey felto i posted the circuit to biuld a logic ic tester sometime ago , serch the forums youll find it