From buffer to amp stage mod. Its possibile to do?

Papabravo

Joined Feb 24, 2006
20,993
And we see that there is no voltage gain. There still may be current gain and/or power gain. I have not work with these GP transistors in that frequency range.
 

Ian0

Joined Aug 7, 2020
9,494
And we see that there is no voltage gain. There still may be current gain and/or power gain. I have not work with these GP transistors in that frequency range.
Only about 15dB, up to about 25MHz, not quite the 20dB (with R1=430Ω R2=47Ω) that 1+R1/R2 says it hypothetically should be, and given that fT is 250MHz for that transistor, about what would be expected.
 

Papabravo

Joined Feb 24, 2006
20,993
Only about 15dB, up to about 25MHz, not quite the 20dB (with R1=430Ω R2=47Ω) that 1+R1/R2 says it hypothetically should be, and given that fT is 250MHz for that transistor, about what would be expected.
Sorry, I meant from the final output stage. Yes, the gain comes from the Class A stage
 

Papabravo

Joined Feb 24, 2006
20,993
The TS asked asked me in a PM what to do with a .model file. I am posting my response to the thread in question because it may be of help to other readers. The original question involved adding a .model file to the \lib directory under Program Files.


No! You should not add to or modify the files in:
C:\Program Files\LTC\LTspiceXVII\lib
The reason is that LTspice uses this as a reference to do updates
There are several things that you can do:

  1. You can import the text of the .model statement onto your schematic as a spice directive
  2. You can place the model file in in the folder along with your schematic and use the spice directive .include With no path given it will look in the current subfolder.
  3. You can use an .include statement and put the \sub folder under My documents. On my machine the path would be C:\Users\Username\Documents\LTspiceXVII\lib\sub
  4. The last alternative is that you can add it to the file for transistors located in C:\Users\Username\Documents\LTspiceXVII\lib\cmp\standard.bjt
It is completely safe to add items to this file in your documents folder because LTspice will not overwrite your additions it will always merge the existing file with the updates, preserving any modifications you have made.

I'm going to post this responses in the thread as well.

Life is too short to sweat the small stuff.
 
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