Strange opamp's output impedance in spice
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I'm simulating this circuit in Micro-Cap, which is the clipping stage of a guitar effect. The opamp model is the "NE-5532"
I want to measure the input and the output impedance. I expected an output impedance closer to zero Ohm, and an input impedance of about 10kOhm, with an "infinite" impedance at 0Hz due to the decoupling capacitor at the input.
Here it is the analysis in Micro-Cap.
As you can see the input impedance (the blue graph) is close to what i expected, but the red graph, which is the output impedance, it's really strange. It's almost 10kOhm, with a peak of almost 1MegOhm, and i can't really explain why.
If i switch the model to a "LF-155" i get a more "reasonable" results, with an output impedance of 1.680E-68 Ohm, which is also strange.
Can you help me? This thing is driving me crazy.
operational-amplifier impedance spice input-impedance single-supply-op-amp
asked 7 hours ago
RawCodeRawCode
183
New contributor
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
I'm simulating this circuit in Micro-Cap, which is the clipping stage of a guitar effect. The opamp model is the "NE-5532"
I want to measure the input and the output impedance. I expected an output impedance closer to zero Ohm, and an input impedance of about 10kOhm, with an "infinite" impedance at 0Hz due to the decoupling capacitor at the input.
Here it is the analysis in Micro-Cap.
As you can see the input impedance (the blue graph) is close to what i expected, but the red graph, which is the output impedance, it's really strange. It's almost 10kOhm, with a peak of almost 1MegOhm, and i can't really explain why.
If i switch the model to a "LF-155" i get a more "reasonable" results, with an output impedance of 1.680E-68 Ohm, which is also strange.
Can you help me? This thing is driving me crazy.
operational-amplifier impedance spice input-impedance single-supply-op-amp
asked 7 hours ago
RawCodeRawCode
183
New contributor
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
$begingroup$
You got the first two graphs from a single run of the simulator?
$endgroup$
– The Photon
7 hours ago
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something's fundamentally broken with this simulator or its NE5532 model. You physically can't have an output voltage of 1 MV
$endgroup$
– Marcus Müller
7 hours ago
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@ThePhoton Yes, this is a single run of the ac analysis
$endgroup$
– RawCode
7 hours ago
$begingroup$
Is that a 10 ohm resistor from output pin to ground (R11?) The op-amp will try to maintain 4.5V across that resistor: too much DC current will flow for the op-amp (smoke would ensue). Try returning that resistor to the 4.5V supply instead of ground.
$endgroup$
– glen_geek
6 hours ago
add a comment |
$begingroup$
I'm simulating this circuit in Micro-Cap, which is the clipping stage of a guitar effect. The opamp model is the "NE-5532"
I want to measure the input and the output impedance. I expected an output impedance closer to zero Ohm, and an input impedance of about 10kOhm, with an "infinite" impedance at 0Hz due to the decoupling capacitor at the input.
Here it is the analysis in Micro-Cap.
As you can see the input impedance (the blue graph) is close to what i expected, but the red graph, which is the output impedance, it's really strange. It's almost 10kOhm, with a peak of almost 1MegOhm, and i can't really explain why.
If i switch the model to a "LF-155" i get a more "reasonable" results, with an output impedance of 1.680E-68 Ohm, which is also strange.
Can you help me? This thing is driving me crazy.
operational-amplifier impedance spice input-impedance single-supply-op-amp
asked 7 hours ago
RawCodeRawCode
183
New contributor
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
I'm simulating this circuit in Micro-Cap, which is the clipping stage of a guitar effect. The opamp model is the "NE-5532"
I want to measure the input and the output impedance. I expected an output impedance closer to zero Ohm, and an input impedance of about 10kOhm, with an "infinite" impedance at 0Hz due to the decoupling capacitor at the input.
Here it is the analysis in Micro-Cap.
As you can see the input impedance (the blue graph) is close to what i expected, but the red graph, which is the output impedance, it's really strange. It's almost 10kOhm, with a peak of almost 1MegOhm, and i can't really explain why.
If i switch the model to a "LF-155" i get a more "reasonable" results, with an output impedance of 1.680E-68 Ohm, which is also strange.
Can you help me? This thing is driving me crazy.
operational-amplifier impedance spice input-impedance single-supply-op-amp
operational-amplifier impedance spice input-impedance single-supply-op-amp
asked 7 hours ago
RawCodeRawCode
183
New contributor
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 7 hours ago
RawCodeRawCode
183
New contributor
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 7 hours ago
RawCode
asked 7 hours ago
RawCodeRawCode
183
New contributor
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 7 hours ago
RawCodeRawCode
183
asked 7 hours ago
RawCodeRawCode
183
183
New contributor
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
RawCode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$begingroup$
You got the first two graphs from a single run of the simulator?
$endgroup$
– The Photon
7 hours ago
$begingroup$
something's fundamentally broken with this simulator or its NE5532 model. You physically can't have an output voltage of 1 MV
$endgroup$
– Marcus Müller
7 hours ago
$begingroup$
@ThePhoton Yes, this is a single run of the ac analysis
$endgroup$
– RawCode
7 hours ago
$begingroup$
Is that a 10 ohm resistor from output pin to ground (R11?) The op-amp will try to maintain 4.5V across that resistor: too much DC current will flow for the op-amp (smoke would ensue). Try returning that resistor to the 4.5V supply instead of ground.
$endgroup$
– glen_geek
6 hours ago
add a comment |
$begingroup$
You got the first two graphs from a single run of the simulator?
$endgroup$
– The Photon
7 hours ago
$begingroup$
something's fundamentally broken with this simulator or its NE5532 model. You physically can't have an output voltage of 1 MV
$endgroup$
– Marcus Müller
7 hours ago
$begingroup$
@ThePhoton Yes, this is a single run of the ac analysis
$endgroup$
– RawCode
7 hours ago
$begingroup$
Is that a 10 ohm resistor from output pin to ground (R11?) The op-amp will try to maintain 4.5V across that resistor: too much DC current will flow for the op-amp (smoke would ensue). Try returning that resistor to the 4.5V supply instead of ground.
$endgroup$
– glen_geek
6 hours ago
$begingroup$
You got the first two graphs from a single run of the simulator?
$endgroup$
– The Photon
7 hours ago
$begingroup$
You got the first two graphs from a single run of the simulator?
$endgroup$
– The Photon
7 hours ago
$begingroup$
something's fundamentally broken with this simulator or its NE5532 model. You physically can't have an output voltage of 1 MV
$endgroup$
– Marcus Müller
7 hours ago
$begingroup$
something's fundamentally broken with this simulator or its NE5532 model. You physically can't have an output voltage of 1 MV
$endgroup$
– Marcus Müller
7 hours ago
$begingroup$
@ThePhoton Yes, this is a single run of the ac analysis
$endgroup$
– RawCode
7 hours ago
$begingroup$
@ThePhoton Yes, this is a single run of the ac analysis
$endgroup$
– RawCode
7 hours ago
$begingroup$
Is that a 10 ohm resistor from output pin to ground (R11?) The op-amp will try to maintain 4.5V across that resistor: too much DC current will flow for the op-amp (smoke would ensue). Try returning that resistor to the 4.5V supply instead of ground.
$endgroup$
– glen_geek
6 hours ago
$begingroup$
Is that a 10 ohm resistor from output pin to ground (R11?) The op-amp will try to maintain 4.5V across that resistor: too much DC current will flow for the op-amp (smoke would ensue). Try returning that resistor to the 4.5V supply instead of ground.
$endgroup$
– glen_geek
6 hours ago
add a comment |
1 Answer
1
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oldest
votes
$begingroup$
In comments you added this information,
this is a single run of the ac analysis
This method won't allow you to measure the input or output (especially the output) impedance accurately.
You need to test the output impedance by applying a source to the output with the input zero'd and vice versa. You will need two separate runs of the simulator to do this.
answered 6 hours ago
The PhotonThe Photon
86k398198
$endgroup$
$begingroup$
You saved my day!
$endgroup$
– RawCode
6 hours ago
add a comment |
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1 Answer
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1 Answer
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$begingroup$
In comments you added this information,
this is a single run of the ac analysis
This method won't allow you to measure the input or output (especially the output) impedance accurately.
You need to test the output impedance by applying a source to the output with the input zero'd and vice versa. You will need two separate runs of the simulator to do this.
answered 6 hours ago
The PhotonThe Photon
86k398198
$endgroup$
$begingroup$
You saved my day!
$endgroup$
– RawCode
6 hours ago
add a comment |
$begingroup$
In comments you added this information,
this is a single run of the ac analysis
This method won't allow you to measure the input or output (especially the output) impedance accurately.
You need to test the output impedance by applying a source to the output with the input zero'd and vice versa. You will need two separate runs of the simulator to do this.
answered 6 hours ago
The PhotonThe Photon
86k398198
$endgroup$
$begingroup$
You saved my day!
$endgroup$
– RawCode
6 hours ago
add a comment |
$begingroup$
In comments you added this information,
this is a single run of the ac analysis
This method won't allow you to measure the input or output (especially the output) impedance accurately.
You need to test the output impedance by applying a source to the output with the input zero'd and vice versa. You will need two separate runs of the simulator to do this.
answered 6 hours ago
The PhotonThe Photon
86k398198
$endgroup$
In comments you added this information,
this is a single run of the ac analysis
This method won't allow you to measure the input or output (especially the output) impedance accurately.
You need to test the output impedance by applying a source to the output with the input zero'd and vice versa. You will need two separate runs of the simulator to do this.
answered 6 hours ago
The PhotonThe Photon
86k398198
answered 6 hours ago
The PhotonThe Photon
86k398198
answered 6 hours ago
The PhotonThe Photon
86k398198
answered 6 hours ago
The PhotonThe Photon
86k398198
86k398198
$begingroup$
You saved my day!
$endgroup$
– RawCode
6 hours ago
add a comment |
$begingroup$
You saved my day!
$endgroup$
– RawCode
6 hours ago
$begingroup$
You saved my day!
$endgroup$
– RawCode
6 hours ago
$begingroup$
You saved my day!
$endgroup$
– RawCode
6 hours ago
add a comment |
RawCode is a new contributor. Be nice, and check out our Code of Conduct.
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$begingroup$
You got the first two graphs from a single run of the simulator?
$endgroup$
– The Photon
7 hours ago
$begingroup$
something's fundamentally broken with this simulator or its NE5532 model. You physically can't have an output voltage of 1 MV
$endgroup$
– Marcus Müller
7 hours ago
$begingroup$
@ThePhoton Yes, this is a single run of the ac analysis
$endgroup$
– RawCode
7 hours ago
$begingroup$
Is that a 10 ohm resistor from output pin to ground (R11?) The op-amp will try to maintain 4.5V across that resistor: too much DC current will flow for the op-amp (smoke would ensue). Try returning that resistor to the 4.5V supply instead of ground.
$endgroup$
– glen_geek
6 hours ago