The resistor for current measurement belongs to the emitter of Q1.
Q3 base emitter and R1 are shorted in your drawing but Q1 receives
some base current through R2.
Look for "VBE referenced current source" schematics.
When simulating anything like this be sure to use models other than the default NPN/PNP ones, particularly for things like output devices. You will find it makes a massive difference to the sim... and not necessarily for the better. For example try the default library 2N3055 for your outputs.
2N3055 has a poor gain at higher currents so it is current limiting before it reaches voltage clipping. So attached is a more realistic circuit using Darlington circuits to make higher currents available. I also added capacitors etc. for a more complete amplifier circuit. The added gain requires a compensation capacitor for stability. Note that the Darlington circuit has an additional junction drop which slightly reduces the clipping amplitude. However, the increase in loop gain reduces the THD to a more acceptable level.
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id need to get the bd 139 spice models first or try using tip41 transistors
which i also need the models of. and im new to ltspice and i dont know how to add them
which i also need the models of. and im new to ltspice and i dont know how to add them
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used whatever medium power transistor that was in the library and got this i also added a current source
Or maybe more like it would in practice 🙂
Indeed so 👍
Try these (file called LT Models). Keep this for reference and copy and paste any models you want out of this and into a new notepad file.
Easy way to begin with...
Put the models you want into a notepad file and save it with a suitable name. Use the 'Find' function in Notepad (click edit to bring this up) to find a model. Copy that model and paste it into the new file.
For example:
I have saved TIP41C and BD139 in the file called 'My Models'. It looks like this:
You must now EITHER keep this file with your .asc (in the same folder) or place the model file somewhere it can be called up.
Lets keep it in the same folder for now.
Next add a directive on the sim to point to the file. So we .include My Models.txt
Now you can right click the text of the 2N3055 and replace with TIP41C
The model name must be identical to how it appears in the file.
You can add as many models as you want to the file but remember to keep the file and the .asc's all in the same folder.
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What I do is add the model file to the root of the C drive. This allows you to have a single file and call it up from any .asc anywhere on your PC.
Add a directive to suit such as this to each of your sims:
