Hey everyone
I try to use op-amp like buffer with single supply. I want to pass through the amplifier sine wave about 30Khz, and 3Vp-p. I try also with 1.5V dc offset and also without dc offset. This is my circuit:


when I measure the signal at the output I see the sine wave but without the parts below 1.5V. something like that:


I don't understand why I didn't get my full sine wave at the output. it is simple implementation of follower op-amp.
I try also to work with vcc supply of 5V but I get same resault.
Thank you very much

 

If you look at the datasheet for a 741, you will see that it requires a total supply voltage of more than 10V.
That’s why it doesn’t work with a supply of 3V or 5V.

 

Also
V3 is not connected to ground.

 

Read the datasheet. LM741 won't operate from a single supply, or one as low as 3.3V. Common mode input range and output voltage swing range will preclude correct operation.

 

The 741 opamp design is 56 years old. It was designed to use a plus and minus 15V supply and works poorly (low slew rate) above 9kHz. Bury it an use a newer and better opamp.

I agree that your opamp rectifies the signal because its input has no DC bias voltage.

 

I try also to work with vcc supply of 5V but I get same resault.

As stated before requires a higher V1.
I breadboarded your circuit and it required a minimum of 7 volts.
You can eliminate V3.

 

Next time read the data sheet.
Real op amps have many limitations that the ideal op amps shown in textbooks don't.

 

The 741 opamp design is 56 years old. It was designed to use a plus and minus 15V supply and works poorly (low slew rate) above 9kHz. Bury it an use a newer and better opamp.

I agree that your opamp rectifies the signal because its input has no DC bias voltage.

INDEED!! The 741 is an antique, save it for repairing some antique electronic devices that have a failed opamp.

 

See

 

Here are your problems with the very old 741 opamp:

 

I am old enough to have worked with the 741’s predecessor, the 709.
For starters, the 709 required an external compensation network. And if the input common mode range or the output was shorted, the device could be damaged.
The 741 was such an incredible upgrade! But that was over 50 years ago.

 

So you can use the 10V minimum spec'd supply with the 741, or a rail-rail I/O op amp that can operate with a 3.3V supply, your choice.

 

Thank you very much!