Why Is My UA741 Op Amp Voltage Follower Not Outputting Correctly?

[JerryG]

I am using a TI uA741CPE4 op amp for a voltage follower, but it's not working correctly.

Here is how I have it connected:

OUT connected to IN-
Input voltage is connected to IN+
Vcc- is connected to ground
Vcc+ is connected to 3.3V

An input voltage of 0 - 1.75v gives a constant output voltage of 1.83v.
From there, the output voltage goes up, but it only goes up to about 3.15v with an input voltage of 3.3v.

I have tried two band new chips, but got the same result with each.

 

[Averagesupernova]

A 741 op-amp is not a rail to rail op-amp. This means that you need the supply voltage to be several volts higher than the highest expected output voltage.

 

[KingNothing]

In other words, if you want the output to swing from 0V to 3.33V, you'll need power supplies of roughly -2V and +5.33V.

 

[AlephZero]

Also, a 3.3V siupply is probably too low to be useful.

The datasheet for a 714C gives the output voltage range as +/-13V typical, with a power supply of +/- 15V. That suggests the output will only swing to 2V inside the power supply voltage,

You seem to be getting a bit more than that. Chips often perform better than the "typical" values on the datasheet, but it's not a good idea to design circuits that rely on that happening.

So you need a minimum of a 5V supply to do anything useful, i.e. if the power rails are 0V and 5V, the output can swing between 2V and 3V.

A 9V battery (i.e. +/- 4.5V) would be a more typical "low voltage" supply for a 714 circuit design.

 

[Xitami]

1968: Release of the μA741