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conanhaha
Joined: 20 Dec 2008
Posts: 9
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 06 Nov 2009 5:12 IC tester for op-amp |
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Hi everyone~
Recently I need to create a circuit with microcontroller based to test IC.
The IC to test at first is 741 op-amp.
Can I know,
What is the basic things that I need to test for 741 op-amp?
What is the tests to be carried on from basic > advance?
How do I test them?
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ark5230
Joined: 29 Jun 2009
Posts: 188
Helped: 15
Location: India
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08 Nov 2009 18:55 Re: IC tester for op-amp |
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One approach is to make a simple amplifier using your op amp (say 741). using a switch or a jumper select two gains (say 1 and 3 or 5). measure the output of the opamp trhough your microcontroller for the two settings of the op amp. If the measured values of gain matches with the expected vaues of gains, the op amp is OK, else it is not good. This may need ADC and also planning the input to the OPAMP. If needed you may include inverting and non inverting input test, this will further increase the circuitary and involve additional concepts.
Raoof
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conanhaha
Joined: 20 Dec 2008
Posts: 9
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09 Nov 2009 14:00 Re: IC tester for op-amp |
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Thx guy 
Now i know i should test it by using either inverting/non-inverting or some circuit like comparator.
Btw, my lecturer told me that with this simple test at first it won't need ADC.
ADC may be needed when further enhance to test the characteristic of the op-amp.
Is that any other way to test the voltage and send to microcontroller to match the output/input to test for close-loop gain?
I mean, how to convert the acceptable gain range (may be+/- 5%) of the output/input so that microcontroller will know and receive the signal?
This is to be done without ADC for now.
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ark5230
Joined: 29 Jun 2009
Posts: 188
Helped: 15
Location: India
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09 Nov 2009 14:13 Re: IC tester for op-amp |
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If you wish to test it in unity gain, assuming 0 (low) or 5 (high) is sufficient to beleive that the OPAMP is working that is fine you dont need to use ADC, just read the status of the output pin of the 741. For other gain conditions and if the output voltage is to be found, you need something like ADC.
Raoof
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conanhaha
Joined: 20 Dec 2008
Posts: 9
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09 Nov 2009 15:18 IC tester for op-amp |
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Thx again for reply.
Btw if i wish to test with higher gain, like 10?
For example my gain should be within the range of 9-11, my input voltage is 5v.
So how to make it possible that when it is within the range of 9-11, mean when it is 45-55v then it will held high while when it is higher or lower then these values will held low?
Is it i need construct some circuit similar to ADC but instead of using ADC i construct it myself?
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ark5230
Joined: 29 Jun 2009
Posts: 188
Helped: 15
Location: India
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12 Nov 2009 16:30 IC tester for 741 op-amp basic vs advanced test |
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It would depend the degree of complexity and flexibility you wish to include in your project. If you go for higher degree of flexibility allowing a wider range of gains, you need to include provisions for doing that.
For example if you are using a gain below 10, the input of OPAMP could be about 0.5V so that at different gain values you can compare the output of OPAMP read via ADC, the maximum value would be 5V with highest gain of 10.
If you wish to have a gain of 0 - 50 say, the input could be 0.1 volt, similar test will prove if it is functioning alright or not. However at lower values of gains say 1, the output will be 0.1V. This means your measuring sensitivity will be limited. The full scale value is 5V and you measure 0.1, this will still be OK if you have ADC better than 8 bit.
Raoof
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