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| op amps using specific power supply configuration eg:+8v/-5v why????????? |
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| ifrenide:
hello, can somebody here tell me why they use specific power supply configuration +8v and -5v for op amps and comparators in some electronic devices instead of using +8v and ground. by the way I found this in a metal detector schematic (TGSL), and that make me confused also about the output of the compartor ,when an AC signal is fed to its inverting output why the out put is not +8vand - 5v Instead the output is +8v and 0v ?????????????????? |O best regards |
| schmitt trigger:
*A probable explanation* The LM358 input common mode range goes all the way to the negative supply, but it must be about 2.5 volts less than the positive supply. Values from memory, check the datasheet for actual values. And I believe its output swing behaves similarly. Thus, to obtain a +/-5 v dynamic range, this trick was required. |
| ifrenide:
ok my brother . lets consider that those op amps is powered with +8v and gnd what difference it make (understanding by using the oposite) :D and I i would like to mention that there are some comparators in the schematic what does this configuration with them ??? thank you best regards |
| StillTrying:
--- Quote from: ifrenide on April 27, 2019, 12:38:33 pm ---when an AC signal is fed to its inverting output why the out put is not +8vand - 5v Instead the output is +8v and 0v best regards --- End quote --- The LM393 comparators will be outputting -5V to nearly +8V. Many of the opamps have +IN connected to 0V and a diode in the feedback to -IN which will stop their output going below -0.7V even though their -Ve supply is -5V. Edit: Now I've looked again the diodes are the wrong way around. :-// |
| ifrenide:
but here in this schematic there is no diode to stop the output going into -5v. if you don't talk about an integrated diode in the the copmarator . best regards |
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