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LTSpice - change display for output voltage

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Boncuk

New Member
Hi,

due to the limited PCI slots available in new mainboards (2) I had to change audio to use the onboard audio amplifier.

It obviously does not contain a mic preampflifier making an external amplifier necessary.

I simulated the circuit using LTSpice, but it displays db.

How can I change the simulation to display output voltage levels? Input voltage from the mic is 30mV/pp and I expect 750mV/pp as a minimum output voltage from the circuit.

Boncuk
 

Attachments

  • PC-MIC-AMPL..zip
    777 bytes · Views: 154
  • PC-MIC-AMPL..gif
    PC-MIC-AMPL..gif
    12.4 KB · Views: 340
  • PC-MIC-AMPL-SIM..gif
    PC-MIC-AMPL-SIM..gif
    18.1 KB · Views: 266
Last edited:
Hi,

due to the limited PCI slots available in new mainboards (2) I had to change audio to use the onboard audio amplifier.

It obviously does not contain a mic preampflifier making an external amplifier necessary.

I simulated the circuit using LTSpice, but it displays db.

How can I change the simulation to display output voltage levels? Input voltage from the mic is 30mV/pp and I expect 750mV/pp as a minimum output voltage from the circuit.

Boncuk

hi Hans,
Look at this edited LTS.asc
Note: the output cap was not connected to the emitter.
I have not changed any thing else, the circuit has severe distortion.

Hans02..gifView attachment PC-MIC-AMPL2..asc
 
hi Hans,
Look at this edited LTS.asc
Note: the output cap was not connected to the emitter.
I have not changed any thing else, the circuit has severe distortion.
Hi Eric,

thank you for your quick reply.

I don't get the plot which is shown in your example. How can I get to that? If I have voltages and wave shape on display I might be able to improve the circuit.

Is there a way to use a certain hFE value for the transistors?

Q1 has to have an hFE of at least 400.

In the real circuit I will use a BC550C (hFE 420-800)

Even speech will be much distorted.

Regards

Hans
 
Last edited:
Hi Eric,

thank you for your quick reply.

I don't get the plot which is shown in your example. How can I get to that? If I have voltages and wave shape on display I might be able to improve the circuit.

Is there a way to use a certain hFE value for the transistors?

Q1 has to have an hFE of at least 400.

In the real circuit I will use a BC550C (hFE 420-800)

Even speech will be much distorted.

Regards

Hans

hi Hans,
Did you run that *.asc file I attached, you should see the same.
AAesp04..gifAAesp05..gif

EDIT:
To SELECT a transistor from the LTS library , place the cursor over the transistor image and right click.
 
Last edited:
Hi Eric,

I simulated the file you posted but I get a completely different display when running the simulation.

How do I get to change function of the oscilloscope?

I downloaded LTSpice today. It is version 4.06 dated March 16th 2010.

Hans
 

Attachments

  • PC-MIC-AMPL-01..asc
    2.8 KB · Views: 163
hi,
Did you change your settings in the panels as shown in my Post #4. images.?


EDIT:
The circuits you have posted are different from the original.?

AAesp06..gif
 
Last edited:
Boncuk's question is "what is the difference between a .AC solution vs a .TRAN solution"?

.AC solves for the DC bias point, then assumes all devices are linear for small signals, and then sweeps the frequency as the independent variable. It uses the AC= spec on sources as the reference level in the db plots.

.TRAN solves for the DC bias point, then varies Time as the independent variable, while all voltages and currents are the dependent variables. It works for large signals, including non-linear behavior. It uses the DC, PULSE, SINE, etc spec on sources for stimulus.

When testing an audio related circuit, I first use a .DC solution to check if the circuit is properly biased. I then use a .TRAN solution to check the dynamic range and onset of clipping. Next I do a .AC solution to sweep the frequency response. Finally, I might do a Temperature sweep and a Noise Analysis. LTSpice can do all of these...
 
Last edited:
Hi Mike,

as I already posted I just installed LTSpice and trying to get familiar with it.

I haven't yet found a button to change simulation display/function.

Regards

Hans
 
Hi Mike,

as I already posted I just installed LTSpice and trying to get familiar with it.

I haven't yet found a button to change simulation display/function.

Regards

Hans

There is NO Menu Pick. Look at the three attached simulations:
 

Attachments

  • D85op.png
    D85op.png
    23.5 KB · Views: 240
  • D85Tr.png
    D85Tr.png
    47 KB · Views: 207
  • D85ac.png
    D85ac.png
    52.7 KB · Views: 215
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