LM741 Single Supply

[D.M.]

Can i use a 12 V DC power supply (0 to +12V) single ended to power my LM741?

Also, if using this to amplify a microphone, can i connect the "hot" lead from the mic to pin 2 (inverting), and the the ground from the mic to pin 3 (non inverting terminal).

Since my power supply is only from 0-12 will this cause problems? <--- Normally the power supply is +/- X volts.. and ground is considered 0 volts or in between both supplies.. In this case i only have 0-12, so can i consider the 0 volt terminal ground as well when connecting my mic?

 

[ericgibbs]

hi,
The best way is to use capactor coupling for the single supply 741.
Look at this PDF for options on how to do this, ask if you cannot follow it.

 

[hkBattousai]

hi,
The best way is to use capactor coupling for the single supply 741.
Look at this PDF for options on how to do this, ask if you cannot follow it.

Can I remove the capacitors C1, C2 and Cout in Figures 2 and 3 in the PDF attached to your message, if I want to run my opamp in DC mode? I think those capacitor are AC coupling capacitors and can be removed in DC mode, is this true?

 

[ericgibbs]

Can I remove the capacitors C1, C2 and Cout in Figures 2 and 3 in the PDF attached to your message, if I want to run my opamp in DC mode? I think those capacitor are AC coupling capacitors and can be removed in DC mode, is this true?

hi,
What voltage signal levels are you planning to amplify.?

 

[audioguru]

A 741 opamp is 42 years old and might not work with a supply as low as 12V.
It is too noisy (hiss) to be used as a mic preamp and its full output frequency response drops above only 9kHz.

Use a low noise wide bandwidth (100 kHz) TL071 audio opamp instead.

A single supply opamp circuit must use all the capacitors shown or its output will be near the positive power supply voltage all the time and it won't amplify anything.

EDIT:
EEK! Don't connect your mic directly to both input pins on an opamp. It has a voltage gain of about 200,000!
The opamp should have negative feedback to reduce its gain to about 200.

 

[hkBattousai]

hi,
What voltage signal levels are you planning to amplify.?

At most +-15V.

 

[ericgibbs]

At most +-15V.

I think you misunderstood my question.

What is the voltage range and polarity of the input signals to the 741?

The 741 is a very old OPA and in a single supply configurationis not able to swing to within about less than +2V of the 0V rail and approx 2 to 3 volts of the +V supply rail.

Please explain your project.

 

[hkBattousai]

I think you misunderstood my question.

What is the voltage range and polarity of the input signals to the 741?

The 741 is a very old OPA and in a single supply configurationis not able to swing to within about less than +2V of the 0V rail and approx 2 to 3 volts of the +V supply rail.

Please explain your project.

I don't have a project in my mind. I just read this topic, and had a look at your PDF file. The single-supply circuits in your file has coupling capacitors, I asked if I could remove those capacitors when working with DC signals. Then you asked what signal levels do I desire to amplify. I prefer the term "process (amplify, attanuate, differentiate, sum, accumulate, etc)" rather than "amplify". And I said "+-15V", I was wrong to mension negative values since we are discussing single-supply opams, but I wanted to mean that I could use any signal level in acceptable range, assumed that opamp is supplied with enough voltage level.

This topic was very good for me, I learned how useless 741 is today, actually I still had hope for that legendary and historical opamp. Now I understand why my all 741 circuits were that much problematic...
So what are the new generation opams that supersede 741? I used LM324 in a recent project, It wasn't good enough but working at least.

 

[audioguru]

The LM324 quad opamps and the LM358 dual opamps are almost as old as the 741 opamp. They were the first "low power single supply opamps" so the designers made them without bias current for their output transistors so their crossover distortion is 3% and their max output frequency is only 2kHz.

For low power single supply opamps with all the spec's of the LM324 and LM358 but without any crossover distortion and a max output frequency of 35kHz I use the MC33171 single opamp, MC33172 dual opamps and MC33174 quad opamps.
For normal power single supply opamps with all the spec's of the LM324 and LM358 opamps but without any crossover distortion and a max output frequency of 100kHz I use the MC34071 single opamp, MC34072 dual opamps and MC34074 quad opamps.

The TL071 single, TL072 dual and TL074 quad opamps are low noise with a max output frequency of 100kHz. They have been used in hi-fi equipment for about 30 years.
The OPA134 single, OPA2134 dual and OPA4134 quad opamps are better with very low noise, distortion as low as 0.00008% and a max output frequency of 220kHz.

 

[wawentz]

Good day to everyone, I'm an ECE student and I'm making an Ultrasonic TxRx circuit,. My receiver part uses LM741 as signal amplifier for the output of the ultrasonic transducer,. Operating frequency is 40KHz,. as mentioned above the output of LM741 is just above 9Khz,. does that mean it is not applicable for my project??

 

[ericgibbs]

Good day to everyone, I'm an ECE student and I'm making an Ultrasonic TxRx circuit,. My receiver part uses LM741 as signal amplifier for the output of the ultrasonic transducer,. Operating frequency is 40KHz,. as mentioned above the output of LM741 is just above 9Khz,. does that mean it is not applicable for my project??

hi,
Read post #9, it explains that the 741 has a VERY poor specification.
Some of the more modern OPA's described will give the results you want at 40KHz and most of them are not expensive, also you can get dual versions.

 

[wawentz]

Thank you sir,. I didn't expect such a fast reply,. I'm trying LM358,. but again, as mentioned earlier it's almost as old as LM741,. =D

Thanks again sir, I'll study TL071,.

 

[atferrari]

hi,

Look at this PDF for options on how to do this, ask if you cannot follow it.

Figure 7 in that document has the battery shortcircuited to ground.

 

[audioguru]

I'm making an Ultrasonic TxRx circuit,. My receiver part uses LM741 as signal amplifier for the output of the ultrasonic transducer,. Operating frequency is 40KHz,. as mentioned above the output of LM741 is just above 9Khz,. does that mean it is not applicable for my project??

As was said above, the lousy old 741 opamp is 43 years old and has almost no output at ultrasonic frequencies.
Use an audio opamp instead that performs well up to 100kHz. I use TL071 single, TL072 dual and TL074 quad audio opamps that are inexpensive and are available almost everywhere.

Here are two graphs from the datasheet of a uA741 opamp. An LM741 opamp is the same.

 

[ericgibbs]

Figure 7 in that document has the battery shortcircuited to ground.

hi atferrari,
Look closely at the text description for fig #7...

Edit.
I have corrected the multiple 'gnds'