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single supply alternative to TL082 op-amp
single supply alternative to TL082 op-amp
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Old 13th June 2019, 04:46 PM   #1
Qualitysound is offline Qualitysound
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Default single supply alternative to TL082 op-amp

Hi All,

I'm thinking of using this circuit to supply audio signal to arduino nano. purpose is to run an arduino based vu meter. arduino only accepts DC 0-5v. Below circuit amplify weak input audio signal & let the audio signal move between DC 0-5V. My problem is, I dont have a dual power supply or batteries to drive this thing. Is it possible to do the same thing using a single power supply ?(preferbaly 5V instead of dual 9V )

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Old 13th June 2019, 04:56 PM   #2
rayma is online now rayma  United States
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Quote:
Originally Posted by Qualitysound View Post
let the audio signal move between DC 0-5V. My problem is, I dont have a dual power supply
or batteries to drive this thing. Is it possible to do the same thing using a single power supply ?
(preferbaly 5V instead of dual 9V )
Yes, you'll need a rail-to-rail 5V op amp. There are many types.
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Old 13th June 2019, 07:29 PM   #3
rayma is online now rayma  United States
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Quote:
Originally Posted by Qualitysound View Post
Is it possible to do the same thing using a single power supply ?(preferbaly 5V instead of dual 9V )
Here is a typical single supply biasing circuit from ADI.
You need 3 DC blocking capacitors: input, output, and for the nfb loop.
Avoiding Op-Amp Instability Problems In Single-Supply Applications | Analog Devices
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Last edited by rayma; 13th June 2019 at 07:35 PM.
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Old 14th June 2019, 01:21 AM   #4
Mark Tillotson is offline Mark Tillotson
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AD8656 is a high performing 5V true rail-to-rail dual opamp, good noise and distortion, high output current. Note 6V is the absolute maximum supply for this chip. Its SMT only so an SOIC8 adaptor breakout board might be needed.

Don't be tempted by the LM358, it doesn't have the full-swing bandwidth for audio, nor is it truly rail-to-rail. It would be fine to generate a virtual ground at 2.5V of course.
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Old 14th June 2019, 01:18 PM   #5
Qualitysound is offline Qualitysound
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Thanks All for the replies.
How about this circuit
its also used to feed in analog audio signal to arduino.
Any disadvantages of this circuit?
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Old 14th June 2019, 01:26 PM   #6
nironiro is offline nironiro  Croatia
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Add capacitor parallel to R8, 47uF or 100uF.
And coupling cap on signal input, after volume potentiometer, before R11.

Disadvanteges maybe: signal will be inverted, if that is important.

Last edited by nironiro; 14th June 2019 at 01:30 PM.
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Old 14th June 2019, 03:18 PM   #7
Mark Tillotson is offline Mark Tillotson
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Yes, that DC-blocking cap is in the wrong place, must come after RV2.


There are also active variable gain circuits using the potentiometer as part of the feedback network.


R15 is 1.5k for some reason? 100 ohms is standard, it protects the opamp from oscillation when driving a capacitive load like a length of cable.
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Old 25th June 2019, 05:07 PM   #8
Qualitysound is offline Qualitysound
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Join Date: Feb 2016
Appreciate All the help I received.
I would also like to connect audio out to 3.3v micro controller (ex:esp8266,esp32)
So I read about op-amp usage.
Now my understanding is,If I supply 3.3V as supply voltage instead of 5V , I would be getting a signal that moves between 0 & +3.3V.
Correct me if I'm wrong. Thanks!
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Old 25th June 2019, 06:09 PM   #9
rayma is online now rayma  United States
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Quote:
Originally Posted by Qualitysound View Post
If I supply 3.3V as supply voltage instead of 5V , I would be getting a signal
that moves between 0 & +3.3V.
Yes, and there are other alternatives as well, if you cannot reduce the 5V.
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Old 25th June 2019, 06:39 PM   #10
Mark Tillotson is offline Mark Tillotson
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Join Date: May 2018
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Quote:
Originally Posted by Qualitysound View Post
Appreciate All the help I received.
I would also like to connect audio out to 3.3v micro controller (ex:esp8266,esp32)
So I read about op-amp usage.
Now my understanding is,If I supply 3.3V as supply voltage instead of 5V , I would be getting a signal that moves between 0 & +3.3V.
Correct me if I'm wrong. Thanks!

Well if you choose an opamp that works with that low a supply, some don't. The AD8656 I mentioned above will work down to 2.7V single supply, but there will be cheaper ones. Don't go for micropower opamps though, they don't have much full-swing bandwidth.


Of course if the audio voltage is large you'll need to arrange enough attenuation before the opamp, so it fits into the available swing.
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