The main problem is simple... the choice of opamp. The 741 is utterly and totally outclassed performance wise and has been for the last 35 years or so 🙂 But its great for learning.
Your first circuit has a voltage gain of 100 and that means the gain of the 741 rolls off very early. The second circuit has a gain of 10 and uses a very decent OPA134. You could use that for all these circuits.
Your second opamp circuit also has another problem that the first one doesn't. Can you see what it is ?
Your first circuit has a voltage gain of 100 and that means the gain of the 741 rolls off very early. The second circuit has a gain of 10 and uses a very decent OPA134. You could use that for all these circuits.
Your second opamp circuit also has another problem that the first one doesn't. Can you see what it is ?
I just spotted something else. Normally when talking of poor response and the 741 we mean at HF but you have a problem at LF too. The input coupling caps are far to small in relation to the 1K input impedance. Try a 10uf instead of the 0.1uf.
oh Im sorry I didn't wrote the topic clear. The LM741 circuit and the tone adjust circuit are taken from some audio website. I changed the opamp to the OPA134. Now I change the coupling capcitor to 100uF and the Low freq response is better. How do I determine the suitable coupling cap without simulation?
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oh I am so dumb. It is just an active high pass op amp circuit and Vout/Vin = 10k/(1k +1/jwC).
The input impedance is 1k which is rather low for most purposes, you don't say what it is intended to amplify.
A major difficulty with this circuit is that at the usual 47-100k input impedance general purpose pre amp the series resistor contributes a large amount of noise.
To calculate an input capacitor just transpose, r = 1/(2pifC).
rcw
A major difficulty with this circuit is that at the usual 47-100k input impedance general purpose pre amp the series resistor contributes a large amount of noise.
To calculate an input capacitor just transpose, r = 1/(2pifC).
rcw
The input cap should be 2uF2, i use tantalum here. Input impedance should be 10K or 47K for phono. Use NE5532 opamp, this is an industry standard.
Mac
The Book Worm - DIY Audio Ebooks and Manuals - Speakers, Moscode Amplifiers, Electronics, Map Reading, Free Capacitor Intro.
Mac
The Book Worm - DIY Audio Ebooks and Manuals - Speakers, Moscode Amplifiers, Electronics, Map Reading, Free Capacitor Intro.
Yeah the response is very similar to using 1k and 100uF. Fc = 1/2*pi*R*C is so right. I am going to use this to amplify signal from a Bluetooth module btw.
1k might be too low and overload your source, again industry standard is 10K. Also use a 10 to 100uF cap on the half supply to pin 3 also 10K resistors are fine here.
Mac
Mac
Just for info i use this as a virtual earth input buffer on my Camm EquiTone preamp with gain set at about 2. Works well with the TA7630p that follows, better than any tone control.
Mac
DIY Preamplifier - The Book Worm
Mac
DIY Preamplifier - The Book Worm
<quote>The LM741 circuit and the tone adjust circuit are taken from some audio website.</quote>
WRONG! The second circuit was stolen from my site ( sound.westhost.com ) and is reproduced here without permission.
Moderator - please remove the image from my site from this thread - I am sick and tired of people stealing my drawings without permission or even the common courtesy of acknowledgement.
WRONG! The second circuit was stolen from my site ( sound.westhost.com ) and is reproduced here without permission.
Moderator - please remove the image from my site from this thread - I am sick and tired of people stealing my drawings without permission or even the common courtesy of acknowledgement.
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