LTSpice - change display for output voltage

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

Boncuk said:

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

Click to expand...

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.

View attachment PC-MIC-AMPL2..asc

ericgibbs said:

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.

Click to expand...

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

Boncuk said:

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

Click to expand...

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


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

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

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.?

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...

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

Boncuk said:

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

Click to expand...

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