OP Amp not amplifying audio signal
$begingroup$
Hi, part of my project requires me to amplify an audio signal coming from an electret condenser microphone which outputs an average of 10mVpp to approximately 2.5Vpp. I Used two cascaded non-inverting TL071 OP-amps since one Op-amp doesn't have enough GBW. The output of the mic is low-pass filtered with a cut-off frequency of around 13kHz.
It works perfectly if I input a signal from the signal generator, the output is as required, however with the signal from the microphone there is no output, just a DC offset which is coupled by the capacitor at the end. I also tried buffering the output form the mic.
Any help would be much appreciated.
EDIT:
Didn't realize the error in the schematic, resistor 1k should be between mic and 5V.
operational-amplifier amplifier audio
asked 9 hours ago
SimonSimon
304
$endgroup$
add a comment |
$begingroup$
Hi, part of my project requires me to amplify an audio signal coming from an electret condenser microphone which outputs an average of 10mVpp to approximately 2.5Vpp. I Used two cascaded non-inverting TL071 OP-amps since one Op-amp doesn't have enough GBW. The output of the mic is low-pass filtered with a cut-off frequency of around 13kHz.
It works perfectly if I input a signal from the signal generator, the output is as required, however with the signal from the microphone there is no output, just a DC offset which is coupled by the capacitor at the end. I also tried buffering the output form the mic.
Any help would be much appreciated.
EDIT:
Didn't realize the error in the schematic, resistor 1k should be between mic and 5V.
operational-amplifier amplifier audio
asked 9 hours ago
SimonSimon
304
$endgroup$
$begingroup$
Is the 1 kohm part at the left of the diagram part of your circuit or part of your model for the microphone? Is it also used when you connect the function generator?
$endgroup$
– The Photon
9 hours ago
$begingroup$
JRE's answer was the solution. You're right about the 1k, my mistake. I edited it
$endgroup$
– Simon
9 hours ago
add a comment |
$begingroup$
Hi, part of my project requires me to amplify an audio signal coming from an electret condenser microphone which outputs an average of 10mVpp to approximately 2.5Vpp. I Used two cascaded non-inverting TL071 OP-amps since one Op-amp doesn't have enough GBW. The output of the mic is low-pass filtered with a cut-off frequency of around 13kHz.
It works perfectly if I input a signal from the signal generator, the output is as required, however with the signal from the microphone there is no output, just a DC offset which is coupled by the capacitor at the end. I also tried buffering the output form the mic.
Any help would be much appreciated.
EDIT:
Didn't realize the error in the schematic, resistor 1k should be between mic and 5V.
operational-amplifier amplifier audio
asked 9 hours ago
SimonSimon
304
$endgroup$
Hi, part of my project requires me to amplify an audio signal coming from an electret condenser microphone which outputs an average of 10mVpp to approximately 2.5Vpp. I Used two cascaded non-inverting TL071 OP-amps since one Op-amp doesn't have enough GBW. The output of the mic is low-pass filtered with a cut-off frequency of around 13kHz.
It works perfectly if I input a signal from the signal generator, the output is as required, however with the signal from the microphone there is no output, just a DC offset which is coupled by the capacitor at the end. I also tried buffering the output form the mic.
Any help would be much appreciated.
EDIT:
Didn't realize the error in the schematic, resistor 1k should be between mic and 5V.
operational-amplifier amplifier audio
operational-amplifier amplifier audio
asked 9 hours ago
SimonSimon
304
asked 9 hours ago
SimonSimon
304
edited 8 hours ago
Simon
asked 9 hours ago
SimonSimon
304
asked 9 hours ago
SimonSimon
304
asked 9 hours ago
SimonSimon
304
304
$begingroup$
Is the 1 kohm part at the left of the diagram part of your circuit or part of your model for the microphone? Is it also used when you connect the function generator?
$endgroup$
– The Photon
9 hours ago
$begingroup$
JRE's answer was the solution. You're right about the 1k, my mistake. I edited it
$endgroup$
– Simon
9 hours ago
add a comment |
$begingroup$
Is the 1 kohm part at the left of the diagram part of your circuit or part of your model for the microphone? Is it also used when you connect the function generator?
$endgroup$
– The Photon
9 hours ago
$begingroup$
JRE's answer was the solution. You're right about the 1k, my mistake. I edited it
$endgroup$
– Simon
9 hours ago
$begingroup$
Is the 1 kohm part at the left of the diagram part of your circuit or part of your model for the microphone? Is it also used when you connect the function generator?
$endgroup$
– The Photon
9 hours ago
$begingroup$
Is the 1 kohm part at the left of the diagram part of your circuit or part of your model for the microphone? Is it also used when you connect the function generator?
$endgroup$
– The Photon
9 hours ago
$begingroup$
JRE's answer was the solution. You're right about the 1k, my mistake. I edited it
$endgroup$
– Simon
9 hours ago
$begingroup$
JRE's answer was the solution. You're right about the 1k, my mistake. I edited it
$endgroup$
– Simon
9 hours ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
Put a large resistor from the + input of the left opamp to ground. Say, like 470kohm.
The DC bias from the microphone is getting through to the opamp. The TL071 has very high impedance inputs. The tiny bit of DC that leaks through the first capacitor is enough to push that input away from 0V. The amplification then drives the output to one of the rails.
Just noticed something else.
The microphone bias is messed up.
You need that 1k resistor between the microphone and 5V
As you've got it, the microphone is trying to pull the 5V source up and down in response to the sound.
Best case, it doesn't work.
Worst case, you've killed the microphone.
answered 9 hours ago
JREJRE
22.9k53875
$endgroup$
2
$begingroup$
Could be bias current from the op amp itself that saturates the caps -- there is no DC path for the bias current. This is less likely, as it works with a function generator.
$endgroup$
– Scott Seidman
9 hours ago
$begingroup$
Thank you so much! I realized there was a problem with the small dc leak from the beginning, I couldn't figure out a way to eliminate it completely. Now it works !!
$endgroup$
– Simon
9 hours ago
$begingroup$
Thanks for pointing out the error on the schematic, it was correctly implemented on the breadboard
$endgroup$
– Simon
9 hours ago
add a comment |
$begingroup$
Of course the + input of the first opamp must have a DC bias of 0V.
IF the mic has an output impedance of ZERO ohms then the 120 ohms resistor and the second 0.1uF capacitor produce a cutoff frequency of about 13kHz. But the mic output impedance is about 2.7k ohms and is in parallel with the 1k resistor powering it so the cutoff frequency (without the 120 ohms resistor) is actually 2192Hz which is very muffled.
The value of the 1k resistor powering the mic should be half the supply voltage (2.5V) divided by the mic current (0.5mA)= 5k ohms. Use 5.1k then re-calculate the lowpass filter capacitor value with the 2.7k resistance of the mic parallel with the 5.1k resistor.
answered 1 hour ago
AudioguruAudioguru
48913
$endgroup$
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Put a large resistor from the + input of the left opamp to ground. Say, like 470kohm.
The DC bias from the microphone is getting through to the opamp. The TL071 has very high impedance inputs. The tiny bit of DC that leaks through the first capacitor is enough to push that input away from 0V. The amplification then drives the output to one of the rails.
Just noticed something else.
The microphone bias is messed up.
You need that 1k resistor between the microphone and 5V
As you've got it, the microphone is trying to pull the 5V source up and down in response to the sound.
Best case, it doesn't work.
Worst case, you've killed the microphone.
answered 9 hours ago
JREJRE
22.9k53875
$endgroup$
2
$begingroup$
Could be bias current from the op amp itself that saturates the caps -- there is no DC path for the bias current. This is less likely, as it works with a function generator.
$endgroup$
– Scott Seidman
9 hours ago
$begingroup$
Thank you so much! I realized there was a problem with the small dc leak from the beginning, I couldn't figure out a way to eliminate it completely. Now it works !!
$endgroup$
– Simon
9 hours ago
$begingroup$
Thanks for pointing out the error on the schematic, it was correctly implemented on the breadboard
$endgroup$
– Simon
9 hours ago
add a comment |
$begingroup$
Put a large resistor from the + input of the left opamp to ground. Say, like 470kohm.
The DC bias from the microphone is getting through to the opamp. The TL071 has very high impedance inputs. The tiny bit of DC that leaks through the first capacitor is enough to push that input away from 0V. The amplification then drives the output to one of the rails.
Just noticed something else.
The microphone bias is messed up.
You need that 1k resistor between the microphone and 5V
As you've got it, the microphone is trying to pull the 5V source up and down in response to the sound.
Best case, it doesn't work.
Worst case, you've killed the microphone.
answered 9 hours ago
JREJRE
22.9k53875
$endgroup$
2
$begingroup$
Could be bias current from the op amp itself that saturates the caps -- there is no DC path for the bias current. This is less likely, as it works with a function generator.
$endgroup$
– Scott Seidman
9 hours ago
$begingroup$
Thank you so much! I realized there was a problem with the small dc leak from the beginning, I couldn't figure out a way to eliminate it completely. Now it works !!
$endgroup$
– Simon
9 hours ago
$begingroup$
Thanks for pointing out the error on the schematic, it was correctly implemented on the breadboard
$endgroup$
– Simon
9 hours ago
add a comment |
$begingroup$
Put a large resistor from the + input of the left opamp to ground. Say, like 470kohm.
The DC bias from the microphone is getting through to the opamp. The TL071 has very high impedance inputs. The tiny bit of DC that leaks through the first capacitor is enough to push that input away from 0V. The amplification then drives the output to one of the rails.
Just noticed something else.
The microphone bias is messed up.
You need that 1k resistor between the microphone and 5V
As you've got it, the microphone is trying to pull the 5V source up and down in response to the sound.
Best case, it doesn't work.
Worst case, you've killed the microphone.
answered 9 hours ago
JREJRE
22.9k53875
$endgroup$
Put a large resistor from the + input of the left opamp to ground. Say, like 470kohm.
The DC bias from the microphone is getting through to the opamp. The TL071 has very high impedance inputs. The tiny bit of DC that leaks through the first capacitor is enough to push that input away from 0V. The amplification then drives the output to one of the rails.
Just noticed something else.
The microphone bias is messed up.
You need that 1k resistor between the microphone and 5V
As you've got it, the microphone is trying to pull the 5V source up and down in response to the sound.
Best case, it doesn't work.
Worst case, you've killed the microphone.
answered 9 hours ago
JREJRE
22.9k53875
edited 9 hours ago
answered 9 hours ago
JREJRE
22.9k53875
answered 9 hours ago
JREJRE
22.9k53875
answered 9 hours ago
JREJRE
22.9k53875
22.9k53875
2
$begingroup$
Could be bias current from the op amp itself that saturates the caps -- there is no DC path for the bias current. This is less likely, as it works with a function generator.
$endgroup$
– Scott Seidman
9 hours ago
$begingroup$
Thank you so much! I realized there was a problem with the small dc leak from the beginning, I couldn't figure out a way to eliminate it completely. Now it works !!
$endgroup$
– Simon
9 hours ago
$begingroup$
Thanks for pointing out the error on the schematic, it was correctly implemented on the breadboard
$endgroup$
– Simon
9 hours ago
add a comment |
2
$begingroup$
Could be bias current from the op amp itself that saturates the caps -- there is no DC path for the bias current. This is less likely, as it works with a function generator.
$endgroup$
– Scott Seidman
9 hours ago
$begingroup$
Thank you so much! I realized there was a problem with the small dc leak from the beginning, I couldn't figure out a way to eliminate it completely. Now it works !!
$endgroup$
– Simon
9 hours ago
$begingroup$
Thanks for pointing out the error on the schematic, it was correctly implemented on the breadboard
$endgroup$
– Simon
9 hours ago
2
2
$begingroup$
Could be bias current from the op amp itself that saturates the caps -- there is no DC path for the bias current. This is less likely, as it works with a function generator.
$endgroup$
– Scott Seidman
9 hours ago
$begingroup$
Could be bias current from the op amp itself that saturates the caps -- there is no DC path for the bias current. This is less likely, as it works with a function generator.
$endgroup$
– Scott Seidman
9 hours ago
$begingroup$
Thank you so much! I realized there was a problem with the small dc leak from the beginning, I couldn't figure out a way to eliminate it completely. Now it works !!
$endgroup$
– Simon
9 hours ago
$begingroup$
Thank you so much! I realized there was a problem with the small dc leak from the beginning, I couldn't figure out a way to eliminate it completely. Now it works !!
$endgroup$
– Simon
9 hours ago
$begingroup$
Thanks for pointing out the error on the schematic, it was correctly implemented on the breadboard
$endgroup$
– Simon
9 hours ago
$begingroup$
Thanks for pointing out the error on the schematic, it was correctly implemented on the breadboard
$endgroup$
– Simon
9 hours ago
add a comment |
$begingroup$
Of course the + input of the first opamp must have a DC bias of 0V.
IF the mic has an output impedance of ZERO ohms then the 120 ohms resistor and the second 0.1uF capacitor produce a cutoff frequency of about 13kHz. But the mic output impedance is about 2.7k ohms and is in parallel with the 1k resistor powering it so the cutoff frequency (without the 120 ohms resistor) is actually 2192Hz which is very muffled.
The value of the 1k resistor powering the mic should be half the supply voltage (2.5V) divided by the mic current (0.5mA)= 5k ohms. Use 5.1k then re-calculate the lowpass filter capacitor value with the 2.7k resistance of the mic parallel with the 5.1k resistor.
answered 1 hour ago
AudioguruAudioguru
48913
$endgroup$
add a comment |
$begingroup$
Of course the + input of the first opamp must have a DC bias of 0V.
IF the mic has an output impedance of ZERO ohms then the 120 ohms resistor and the second 0.1uF capacitor produce a cutoff frequency of about 13kHz. But the mic output impedance is about 2.7k ohms and is in parallel with the 1k resistor powering it so the cutoff frequency (without the 120 ohms resistor) is actually 2192Hz which is very muffled.
The value of the 1k resistor powering the mic should be half the supply voltage (2.5V) divided by the mic current (0.5mA)= 5k ohms. Use 5.1k then re-calculate the lowpass filter capacitor value with the 2.7k resistance of the mic parallel with the 5.1k resistor.
answered 1 hour ago
AudioguruAudioguru
48913
$endgroup$
add a comment |
$begingroup$
Of course the + input of the first opamp must have a DC bias of 0V.
IF the mic has an output impedance of ZERO ohms then the 120 ohms resistor and the second 0.1uF capacitor produce a cutoff frequency of about 13kHz. But the mic output impedance is about 2.7k ohms and is in parallel with the 1k resistor powering it so the cutoff frequency (without the 120 ohms resistor) is actually 2192Hz which is very muffled.
The value of the 1k resistor powering the mic should be half the supply voltage (2.5V) divided by the mic current (0.5mA)= 5k ohms. Use 5.1k then re-calculate the lowpass filter capacitor value with the 2.7k resistance of the mic parallel with the 5.1k resistor.
answered 1 hour ago
AudioguruAudioguru
48913
$endgroup$
Of course the + input of the first opamp must have a DC bias of 0V.
IF the mic has an output impedance of ZERO ohms then the 120 ohms resistor and the second 0.1uF capacitor produce a cutoff frequency of about 13kHz. But the mic output impedance is about 2.7k ohms and is in parallel with the 1k resistor powering it so the cutoff frequency (without the 120 ohms resistor) is actually 2192Hz which is very muffled.
The value of the 1k resistor powering the mic should be half the supply voltage (2.5V) divided by the mic current (0.5mA)= 5k ohms. Use 5.1k then re-calculate the lowpass filter capacitor value with the 2.7k resistance of the mic parallel with the 5.1k resistor.
answered 1 hour ago
AudioguruAudioguru
48913
answered 1 hour ago
AudioguruAudioguru
48913
answered 1 hour ago
AudioguruAudioguru
48913
answered 1 hour ago
AudioguruAudioguru
48913
48913
add a comment |
add a comment |
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$begingroup$
Is the 1 kohm part at the left of the diagram part of your circuit or part of your model for the microphone? Is it also used when you connect the function generator?
$endgroup$
– The Photon
9 hours ago
$begingroup$
JRE's answer was the solution. You're right about the 1k, my mistake. I edited it
$endgroup$
– Simon
9 hours ago