TL071 Op Amp problems - help needed

[Ducados]

TL071 Op Amp problems

Anyone know how to wire this up?

All I seem to get is a faint crackle as an output, maybe I'm expecting too much.

I've got 12v going to pin 7, output from pin 6, input to pin 3, ground to pin 4.

 

[FvM]

TL071 Op Amp problems

If you intend a V=+1 buffer, you have to connect additional pin 2 to pin 6. Because TL071 isn't a rail-to-rail OP, the output voltage range is limited however.

 

[betwixt]

As FvM ponts out, it sounds like you are pushing the output to the supply rails already and you probably want to A. Control its gain and B. center the output at half supply potential, you are not doing either at the moment.

Another point is: how are you detecting the crackle? If you have a loudspeaker attached to the output you are using the wrong kind of amplifier altogether.

Brian.

 

[Ducados]

As FvM ponts out, it sounds like you are pushing the output to the supply rails already and you probably want to A. Control its gain and B. center the output at half supply potential, you are not doing either at the moment.

Another point is: how are you detecting the crackle? If you have a loudspeaker attached to the output you are using the wrong kind of amplifier altogether.

Brian.

There's some gain if I disconnect the input and touch pin 3 I get a buzz, but as soon as I earth the input there's nothing. I've got a small speaker attached. Thanks anyway.

 

[Audioguru]

an opamp can drive a load as low as 2 thousand ohms. But an 8 ohm speaker is like a dead short to its output.

The TL071 opamp does not work if its input is earthed (0V) and it does not have positive and negative supplies.

You need a power amplifier like a little LM386 to drive an 8 ohm speaker in the circuit shown on the datasheet of the LM386.

 

[FvM]

Use a verified manufacturer application circuit instead of trying meaningless stuff.

 

[Ducados]

an opamp can drive a load as low as 2 thousand ohms. But an 8 ohm speaker is like a dead short to its output.

The TL071 opamp does not work if its input is earthed (0V) and it does not have positive and negative supplies.

You need a power amplifier like a little LM386 to drive an 8 ohm speaker in the circuit shown on the datasheet of the LM386.

The speaker was the problem. I just needed to establish the device was operational before I proceeded. Thanks.

Added after 2 minutes:

Use a verified manufacturer application circuit instead of trying meaningless stuff.

I intend to continue trying meaningless stuff, it's a good way of learning. Thanks anyway.

 

[FvM]

I intend to continue trying meaningless stuff, it's a good way of learning.

Yes, to a certain degree.

My answer was particularly dedicated to your last post, that sounds rather confused, compared to the basically meaninful first question.

There's some gain if I disconnect the input and touch pin 3 I get a buzz, but as soon as I earth the input there's nothing.

It's also O.K. to try things like this, but I think, it's not a useful level to discuss it at edaboard, e.g. "When I put my finger on the green pin, I hear a hum, but on the red one, there is nothing, can you explain why?"