op-amp 741 o/p troubles.no swing even with ac i/p and stedy fixed nonzero without i/p

[saur]

i had checked the inputs of my op-amp 741 IC and found then to be zero.....but my op-amp still gives an output of 1.88V...whats this that is happening?...
I am using it as a non.inverting type...with +5V Vcc (pin 7)and GND at -Vcc(pin 4)....
I've got to read it from some net articles that....we can use an op-amp(741) with +5V and GND....without using -5V.....so I'm using it that way....

 

[srizbf]

when you are using 741 with single supply(+5v and ground) only ,
you must have proper biasing.

you cannot straight away use a standard non-inv amp ckt that you come across.

post your circuit diagram to give suggestions by members of this forum.

 

[keith1200rs]

I would suggest you use a decent opamp if you want to use a single 5V supply. I cannot remember the input/output range of a 741 but from a single 5V supply I suspect it is next to nothing. The minimum recommended supply is 10V according to TI.

Keith

 

[D.A.(Tony)Stewart]

Consider OA has a gain of a million or more, you can expect input difference must be zero. But you must obey linear range for inputs near V+/V-. So you cannot use 741 @ 5V. If you need to run at V- or gnd on input, consider FET input device. But if you really wanted to use something with a single supply that does not accept input within say 1.6V of supply rails, then you use a pull-up resistor divider on both inputs so that the difference voltage is 0 for input at 0 but the common mode voltage is V+/2. ( short description ) For better CMMR or common mode rejection ratio, consider Instrument Amp config such as this IC https://www.analog.com/static/imported-files/data_sheets/AD620.pdf

OMG , we used uA741's in 1970. ( old technology but works for learning. )

 

[FvM]

we used uA741's in 1970. ( old technology but works for learning. )

In older days, everyone knew about bipolar supply requirements of standard OP types. Somehow engineering knowledge seems to vanish...

 

[surz90]

i think it happen because the output of your 741 circuit is in saturation voltage of Vee.
your output should be 0V, but min and max output from 741 can't produce voltage same with Vee and Vcc.
the maximum output of 741 approximately is (Vcc - 2) V and minimum output is (Vee + 2).
so your output 741 can't be zero if you give 0V to Vee. it will approximately 2V and you get 1.88V at the output.

 

[D.A.(Tony)Stewart]

The Classic uA741 has 22 transistors of which 5 stages are cascaded cross the bipolar supply on the front end to make a current sourcing, reversal protection, cascode amplifier etc, so its not a small single supply choice. Consider +/-10V a typical minimum supply for normal operation. Read the specs.

Search for "single supply low voltage OP AMPs rail-to-rail output" and expect to pay more, or consider using a CMOS inverter with feedback ratio cct.
My 1st hit on google was this https://www.analog.com/static/imported-files/data_sheets/AD820.pdf
Op Amps are easy to use but you still need to learn the limitations in the specs and understand them.