Hi, I'm new to opamps and I can't figure out how to build an amplification circuit. I read a lot about inverting and non inverting circuits, and checked schematics, plus ua741 datasheet, but I'm super confused.
I am trying to build a DC single power supply opamp amplification circuit (I dont know how to use AC currents anyway). That means I can power my opamp with V+ connected to VCC (say 5v from Arduino) and V- to GND right? (since it's DC and not AC, I believe V- pin is GND because input pins are DC sources and are not going to be negative relative to ground)
I am not trying to implement any specific application for now, I just want to be able to amplify a DC voltage going in the non inverting input pin of the opamp, with a gain of more than 1, so the output is more than the input V.
I can't make the circuits I found online work.. I guess there is something about the V-, VCC and input voltages I don't understand. Plus, most of the circuits I found seem to use AC signal sources... I dont know if that means their opamp is powered with AC VCC too but that's something I dont grasp.
Anyway, can someone share a simple circuit of what they would do to amplify a DC signal (I don't know if it needs to be pulsing?? lets say a constant voltage signal for now)? I just want to make a first circuit work so I can start understanding opamps better. Thanks!!
Do not use a 741 op-amp, they were new in 1967, these days they are obsolete and you can not use them very successfully with an Arduino because they need a minimum of +/- 6V, which is a 12V supply.
The 741 is a good learner's tool but, at a supply
voltage of only 5 volts, its output can only swing
over a 2.5 volt (or so) range. As Mike said, you
should use a higher supply voltage.
Herb
herbschwarz:
The 741 is a good learner's tool but, at a supply
voltage of only 5 volts, its output can only swing
over a 2.5 volt (or so) range. As Mike said, you
should use a higher supply voltage.
Herb
No read the data sheet 5V is insufficient to power this op-amp.
Grumpy_Mike:
No read the data sheet 5V is insufficient to power this op-amp.
Thanks, however I can use it with a bench power supply if 5v isnt enough. I really just want to make a single working circuit, so i dont mind if its obsolete. As you said, 741 is a nice learning tool! Yet I cant make a single dc circuit work.
Yeah its a good learning tool, you can find many circuits online, just google UA741, it's not that difficult to operate. If you are not good with electronics then try any simulation software like Proteus. Design and test your circuit on Proteus first and then design it on hardware.
oswe:
what gain are you willing to have with 741 ?try a low gain circuit otherwise will saturate quickly.
check multisim page and simulate as well
Any gain that isnt 1. I only found follower circuits.. I cant manage to have any dc voltage amplified..
jackthom41:
Yeah its a good learning tool, you can find many circuits online, just google UA741, it's not that difficult to operate. If you are not good with electronics then try any simulation software like Proteus. Design and test your circuit on Proteus first and then design it on hardware.
When I google, I only get AC voltage examples. I really want to find an example with DC current so I can try it at home. Thanks!
You will only be wasting your time with the ua741. It simply won't work as you might expect.
Shop on line for a rail-to-rail, single supply op amp guaranteed to work on 5V or less. There are many to choose from, but if you are really stuck, here is a randomly chosen example (disclaimer: I've never used this particular one, but the specs are good).
jremington:
You will only be wasting your time with the ua741. It simply won't work as you might expect.
Shop on line for a rail-to-rail, single supply op amp guaranteed to work on 5V or less. There are many to choose from, but if you are really stuck, here is a randomly chosen example (disclaimer: I've never used this particular one, but the specs are good).
Please, I am just looking for a working non inverting or inverting amplifier circuit with the ua741, even if its a useless circuit. I am not looking for a useful opamp, since I am going to use PSoC for my project. I just want to make a dc amplifier with ua741 no matter if its useless, i just cant find anything that works.
The 741 needs a split power supply. That means one with a positive, ground and negative connection. If you only have a single supply you have to make your ground with two equal size resistors between the power rails, and put a 10uF or so capacitor across each resistor.
Connect the 741’s plus input to this ground. Connect the negative input to to the output with a 10K resistor. Connect the negative input also to a 4K7 resistor. The other end is is the amplifier input. Apply a voltage to this input of say two volts with respect to your made ground.
This is an inverting with a gain of 10 / 4.7. So your output will be 4 volts below the made ground. Note this will require at least a 12V power supply.
For a look at the schematic for this see:-
Note it doesn’t show the made ground part it assumes you know that.
JCSB:
I just want to make a dc amplifier with ua741 no matter if its useless, i just cant find anything that works.
Come on, make up your mind!
You can have a circuit which is useless - "useless" meaning it does not work - which is what people have been telling you, so what is the good of that?
Or do you actually want something that works? If so, you have two choices. Use a suitable op-amp which is clearly not a 741, or use a plus 12 V and minus 12 V power supply for your 741.
The 741 needs a split power supply. That means one with a positive, ground and negative connection. If you only have a single supply you have to make your ground with two equal size resistors between the power rails, and put a 10uF or so capacitor across each resistor.
Connect the 741’s plus input to this ground. Connect the negative input to to the output with a 10K resistor. Connect the negative input also to a 4K7 resistor. The other end is is the amplifier input. Apply a voltage to this input of say two volts with respect to your made ground.
This is an inverting with a gain of 10 / 4.7. So your output will be 4 volts below the made ground. Note this will require at least a 12V power supply.
Note it doesn’t show the made ground part it assumes you know that.
Perfect!! I made this work, this is what I needed. I never realized I needed the -V even with DC, that's why I kept getting a gain of 1 no matter what I tried. Thanks a lot!
jremington:
Sorry I bothered to post!
Hahaha sorry if my reply sounded rude it wasn't intended. You helped me out a few times on some of my older posts and I am very thankful for that
I find the quickest/easiest way to power an ancient opamp like that is two PP3 9V batteries for a +/-9V supply, enough to get about +/-6V of useable input and output swing.
But these days I tend to use things like the AD8656 which run from a single 5V supply, are rail-to-rail and great performance.
Note that people often use the LM358 rail-to-rail opamp, but note its got very low bandwidth, not enough for an audio signal.
