From my knowledge the electret can output up to max 50mV for human voice. I need to preamp this signal to the level of the A2D input (between 0 to 5V). My power supply is monopolarity of 3V or 3.3V or 5V.
Gain 1V
I will need to low pass filter so I will simply use a capacitor in parallel with a resistor that connects between input of opamp and output of opamp.
LPF fc 4kHz so that my A2D can sample at 8kHz.
What are some MODERN opamps that can provide gain up 100 and has a frequency response excellent for audio.
Here are some I found, but I don't know about how solid they really are, hopefully someone is experienced:
TLC272
LM386
LM358
TL071
TL072
TL074
More Modern:
OPA627
LM6172
OPA344
I know there are a lot of threads, but generally they don't mention the amplification they are looking for, I am hoping I can amplify to full resolution (5V). Also, a lot of designs are with opamps that I found out are old and noisy.
Thanks!
Gain 1V
I will need to low pass filter so I will simply use a capacitor in parallel with a resistor that connects between input of opamp and output of opamp.
LPF fc 4kHz so that my A2D can sample at 8kHz.
What are some MODERN opamps that can provide gain up 100 and has a frequency response excellent for audio.
Here are some I found, but I don't know about how solid they really are, hopefully someone is experienced:
TLC272
LM386
LM358
TL071
TL072
TL074
More Modern:
OPA627
LM6172
OPA344
I know there are a lot of threads, but generally they don't mention the amplification they are looking for, I am hoping I can amplify to full resolution (5V). Also, a lot of designs are with opamps that I found out are old and noisy.
Thanks!
Supply voltage is your limiting factor.
You are going to need an opamp specified for >3.3 and with "rail to rail" output capability. You would have to check the data sheets for minimum supply but many of those listed won't do. I don't the LM6172 and OPA344 off hand.
Why not check out Linear Technology where you can specify minimum supply voltages.
Linear Technology - Home Page
Goto signal conditioning and opamps and then specifiy your requirements. Look for rail to rail output too.
You are going to need an opamp specified for >3.3 and with "rail to rail" output capability. You would have to check the data sheets for minimum supply but many of those listed won't do. I don't the LM6172 and OPA344 off hand.
Why not check out Linear Technology where you can specify minimum supply voltages.
Linear Technology - Home Page
Goto signal conditioning and opamps and then specifiy your requirements. Look for rail to rail output too.
Agree and add: if you want 0-5V output ... you need *at* least 5V supply 
And in practice quite a bit more, because "Rail to Rail" Op Amps are not exactly meant for 5V rail voltage, and the one which is *designed* for that, the LM358, is not exactly a star performer .... and distorts more than usual.
Yet it might fit the bill, you need only 4 KHz bandwidth so apparently that's not a Hi Fi application.
Can you detail a little more what you want to do?
And in practice quite a bit more, because "Rail to Rail" Op Amps are not exactly meant for 5V rail voltage, and the one which is *designed* for that, the LM358, is not exactly a star performer .... and distorts more than usual.
Yet it might fit the bill, you need only 4 KHz bandwidth so apparently that's not a Hi Fi application.
Can you detail a little more what you want to do?
Agree and add: if you want 0-5V output ... you need *at* least 5V supply
And in practice quite a bit more, because "Rail to Rail" Op Amps are not exactly meant for 5V rail voltage, and the one which is *designed* for that, the LM358, is not exactly a star performer .... and distorts more than usual.
Yet it might fit the bill, you need only 4 KHz bandwidth so apparently that's not a Hi Fi application.
Can you detail a little more what you want to do?
I can use a 9v battery as supply. I now have two types of op amps LM356 and LM386. I cannot manage to find better op amps locally.
I need to record audio into microprocessor and play it back. Need quality sufficient for speech, just a project. So I need to process the electret microphone signal into the ATD range which is 0v to 5v.
I am able to amplify using lm386 with 100 gain and it appears output can drive a 8ohm speaker but oscilloscope shows that max output is 200mv and the signal goes to negative range.
Can anyone confirm what the output of electret is? How do I simulate this in multisim? Currently it seems my knowledge on this microphone is faulty.
I need a way to verify my circuit so I can attempt to sample and store audio for playback.
Try to get LM358, which is very common and cheap.
Download its datasheet.
Post the circuit you are attempting to build.
LM386 is a power amp, designed to drive a speaker, , it's not an Op Amp.
And the electret must be properly powered, as Chris suggests.
To check both electret and preamp, build it in a Protoboard and power it from 9V battery.
Better than simulation because results are real and with the Electret you actually have, not a generic one .
In fact I'm not even sure an Electret model exists.
And even if it does, not sure it matches yours.
EDIT:
"Planet Earth" , "Universe" or "3RS" (third rock from the Sun) sound cool but don't help much
Download its datasheet.
Post the circuit you are attempting to build.
LM386 is a power amp, designed to drive a speaker, , it's not an Op Amp.
And the electret must be properly powered, as Chris suggests.
To check both electret and preamp, build it in a Protoboard and power it from 9V battery.
Better than simulation because results are real and with the Electret you actually have, not a generic one .
In fact I'm not even sure an Electret model exists.
And even if it does, not sure it matches yours.
EDIT:
To get useful help, please update your Info page and show where you live.
"Planet Earth" , "Universe" or "3RS" (third rock from the Sun) sound cool but don't help much
Last edited:
Try to get LM358, which is very common and cheap.
Download its datasheet.
Post the circuit you are attempting to build.
LM386 is a power amp, designed to drive a speaker, , it's not an Op Amp.
And the electret must be properly powered, as Chris suggests.
To check both electret and preamp, build it in a Protoboard and power it from 9V battery.
Better than simulation because results are real and with the Electret you actually have, not a generic one .
In fact I'm not even sure an Electret model exists.
And even if it does, not sure it matches yours.
EDIT:
To get useful help, please update your Info page and show where you live.
"Planet Earth" , "Universe" or "3RS" (third rock from the Sun) sound cool but don't help much
I got the LM386 actually because I heard it is bad for this but needed to play the audio out once it is processed by the microprocessor board (audio -> LM358 -> A2D -> microprocessor -> D2A -> LM386 -> Speaker)
I have actually physically built the circuit using LM358, it can drive the speaker but obviously not loud. I only connected to the speaker to test it. I put the output on oscilloscope and it was not good, it had max 200mV pk-pk. And I had a minimum voltage which was negative, but microprocessor cannot handle that, needs to be between 0 to 5V. I thought I had it sufficiently biased, should I change the voltage divider in the circuit below to center at 2.5V?
How much current would that electret need? I have a 10k resistor from a 9V source. I will try at 2.2k resistor from 5V the moment I get home.
update:
tried 2.2k with 5v to bias current electret: performance worse as speaker is barely driven now. Resorted back to 10k with 9v.
Came up with the idea to disconnect speaker and connect oscilloscope, thinking speaker is interfering with getting a reading. I can now get voltages pk-pk that is within range for normal speech, it stays between 0.4v to 5v as long as I don't shout or get too close.
There is one issue. I can see the Vmin on the oscilloscope get as low as -1v to -1.9v on normal speech. I want to center the signal at 2.5V, do I have to change resistor r1 and r1? How do I find the DC level and adjust it?
BTW: seems the like the electret gives pk-pk voltage 50mV to 200mV.
tried 2.2k with 5v to bias current electret: performance worse as speaker is barely driven now. Resorted back to 10k with 9v.
Came up with the idea to disconnect speaker and connect oscilloscope, thinking speaker is interfering with getting a reading. I can now get voltages pk-pk that is within range for normal speech, it stays between 0.4v to 5v as long as I don't shout or get too close.
There is one issue. I can see the Vmin on the oscilloscope get as low as -1v to -1.9v on normal speech. I want to center the signal at 2.5V, do I have to change resistor r1 and r1? How do I find the DC level and adjust it?
BTW: seems the like the electret gives pk-pk voltage 50mV to 200mV.
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