I wanted to create a comparator circuit with UA741CN which is only comparator/op-amp I have in my junk right now. I wanted to use it with 5V but no matter what is inverting ref voltage is giving any voltage to non-inverting output gives me always high as output. When I set the power supply to the 8V it works as it should be. Even in 7V it is acting weirdly as i said so. What might be the problem here?

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    \$\begingroup\$ Did you check the 741 datasheet for its (minimum) power voltage(s) requirements? \$\endgroup\$ – Wouter van Ooijen Feb 13 '17 at 20:48
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    \$\begingroup\$ The 741 can't operate on a single 5V supply. It needs its inputs and outputs to all stay a couple of volts away from the power rails. Leaves you with very little to work with at 5V. \$\endgroup\$ – JRE Feb 13 '17 at 20:50
  • \$\begingroup\$ I hooked up 10V for V+ and 0V for V- but max 5V for inverting and non-inverting inputs? These two inputs are also included in Supply Voltage range? \$\endgroup\$ – Bciceksoy Feb 13 '17 at 20:57

Read the datasheet for the device ...the device is unsuitable for your purpose.

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The recommended minimum supply voltage is +/-10 V.

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  • \$\begingroup\$ Actually I tryed this; I supplied 10V to the V+ and 0V to the V- and through voltage divider to the inverting input and connected a potantiometer to the non-inverting input. Still acting abnormal. Is the Supply Voltage information in the datasheet refers also for the inverting and non-inverting inputs? Or just for V+/V-? \$\endgroup\$ – Bciceksoy Feb 13 '17 at 20:54
  • \$\begingroup\$ @user3554877 The supply voltages are V+ and V-. Usually the inverting and non-inverting inputs of an op amp must not exceed the supply voltages. Page 4 of the linked datasheet confirms that's the case for this op amp. \$\endgroup\$ – Null Feb 13 '17 at 21:03
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    \$\begingroup\$ I should probably buy a 5V suitable op-amp or comparator. \$\endgroup\$ – Bciceksoy Feb 13 '17 at 21:09
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    \$\begingroup\$ @Bciceksoy ±10 does not mean "approximately 10". It means "+10 and -10". So +10 on the V+ supply and -10 on the V- supply. \$\endgroup\$ – brhans Feb 13 '17 at 21:44
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    \$\begingroup\$ For clarification: ±10V means a total supply voltage of 20V between the positive and negative supply rails, regardless of where "ground" is. \$\endgroup\$ – MarkU Feb 14 '17 at 1:30

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