# 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 )

Last edited:

#### MrChips

Joined Oct 2, 2009
30,921
Bonjour. Welcome to AAC!
Is this homework?

Thread Starter

#### Philou42

Joined Oct 30, 2023
24
Bonjour. Welcome to AAC!
Is this homework?
It's mixed between Homework and actual work, i'm working at STmicroelectronics while i'm an engineering student. Its a work that i will show at my school and at my work team

#### 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

#### MrChips

Joined Oct 2, 2009
30,921
What is shown is a 2-stage amplifier, not a Darlington amplifier.

#### 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
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?
It's not considerated as 2 stages, because the two transistors are not statically isolated

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?

Thread Starter

#### Philou42

Joined Oct 30, 2023
24
You are going against convention. What authority says they have to be 'statically isolated' to be regarded as separate stages?
My teacher... I only need to build an amplifier with 2 NPN, wich are not isolated statically

#### schmitt trigger

Joined Jul 12, 2010
916
Hmmm…. Perhaps something is lost in the translation, but what do you mean by statically isolated?
Never have heard the term.

Thread Starter

#### Philou42

Joined Oct 30, 2023
24
Hmmm…. Perhaps something is lost in the translation, but what do you mean by statically isolated?
Never have heard the term.
I mean... Just separated by a condensator

#### BobTPH

Joined Jun 5, 2013
9,109
That is called DC coupling between the stages, it does not make it a single stage.

#### 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 )

#### Alec_t

Joined Sep 17, 2013
14,368
how should i express Vs/Ve
Where is Ve?
What is the purpose of RB22?