Amplifier of a voltage gain on 1000 using 2 NPN

Thread Starter

Philou42

Joined Oct 30, 2023
24
Hello everyone,
I need to build an amplifier with a voltage gain of 1000, and the fact is that i need to use 2 NPN 2N2222, and they must be in one stage.
I tried some design around a Darlington pair, and even invented on myself. With the simulation, i effectively can find an voltage gain of 1000, but i can't find it by calculations...

Here is the build i made.
If you have ideas or other builds to propose, i would taking it !
Ve is 1uV !! My mistake.. I need to express Vs / Ve ( Vs is taken at the CQ2 )
1698669355436.png
 
Last edited:

MrChips

Joined Oct 2, 2009
30,921
I would split the gain into two stages, for example, 50 x 20.
Do you know how to design a single stage common emitter BJT amplifier?
 

Thread Starter

Philou42

Joined Oct 30, 2023
24
I would split the gain into two stages, for example, 50 x 20.
Do you know how to design a single stage common emitter BJT amplifier?
Yeah, that would be the best thing to do. The fact is that the 2 NPNs must be in one stage (like a darlington pair or the circuit on the image). That's why i'm struggling with calculations
 

Papabravo

Joined Feb 24, 2006
21,254
Yeah, that would be the best thing to do. The fact is that the 2 NPNs must be in one stage (like a darlington pair or the circuit on the image). That's why i'm struggling with calculations
Excuse me for living, but the schematic in your diagram shows a 2 stage amplifier. Is it possible you have a basic misunderstanding of what a stage is?
 

Thread Starter

Philou42

Joined Oct 30, 2023
24
What is shown is a 2-stage amplifier, not a Darlington amplifier.
Yes, i tried with a darlington pair, but couldn't go superior than 30dB of gain. Also the one on the picture is not considerated as a 2 stage amplifier, because the two transistors are not statically isolated
 

Alec_t

Joined Sep 17, 2013
14,368
Also the one on the picture is not considerated as a 2 stage amplifier, because the two transistors are not statically isolated
You are going against convention. What authority says they have to be 'statically isolated' to be regarded as separate stages?
 

crutschow

Joined Mar 14, 2008
34,671
What is the required frequency response of the amp?

Note: The curved lines on your schematic are cute, but you need to put dots on all the junctions that are connected.
 

Thread Starter

Philou42

Joined Oct 30, 2023
24
That is called DC coupling between the stages, it does not make it a single stage.
Okey, my bad... But it doesnt answer my question at all... How can i express Vs/Ve of this circuit ? Or, if it's not possible, what is the best solution, to have a voltage gain of 1000, without " DC coupling between the stages "... Thx !
 

Thread Starter

Philou42

Joined Oct 30, 2023
24
What is the required frequency response of the amp?

Note: The curved lines on your schematic are cute, but you need to put dots on all the junctions that are connected.
I just need to have 60 dB at 1kHz ( sorry for the dots, everywere the lines are crossing, there is a dot )
 
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