EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ocset on November 14, 2017, 09:11:10 pm
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Hello,
The following two opamp circuits (schematic attached) are exactly the same except for the fact that one has a 5V single supply and the other has a +/-5V dual supply. They both have the same shape of input signal which is also shown attached.
The opamps are LT1013's (not MCP6001s as i stupidly previously said)
LT1013 datasheet:
http://cds.linear.com/docs/en/datasheet/10134fe.pdf (http://cds.linear.com/docs/en/datasheet/10134fe.pdf)
(MCP6001 datasheet deleted)
If the circuit is made on a PCB, will the outputs be exactly the same for each of the circuits?
LTspice simulation also attached but it is not thought that it will be completely accurate
8)
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If the circuit is made on a PCB, will the outputs be exactly the same for each of the circuits?
No, because the +-5V powered MCP6001 will release magic smoke, as its absolute maximal power supply is 7V.
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Thanks, sorry, i meant LT1013 opamps, ive now edited the top post
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If the circuit is made on a PCB, will the outputs be exactly the same for each of the circuits?
Of course not.
In the single supply version, the output of U1 cannot reach zero volt(only within ~60mV) as with the same for U2 output. It is the main reason why people opt to use dual supplies if they want a true zero volt output.
LTspice simulation also attached but it is not thought that it will be completely accurate
8)
If the simulation results differs from your expectation, as is in this case, and you infer that it is the limitation of LTspice, then you are shifting the blame.
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If your input signal is never going to go negative, you can use a single supply opamp. However as others have said, the output will not go completely to 0V.. the LT1013 will get pretty close though as it is specified for single rail usage. Many opamps are not "rail to rail" though.