Two Transistor Amplifier

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JoelM81

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Joined 2007
sawreyrw said:
This circuit will have a gain of 10.
Click to expand...

How do you calculate the gain? It looks to me as 2 common-emitter circuits connected with the output going back into the first stage to act as negative feedback, which in my simulations leads to more linear amplification than if there were no feedback, right? But I'm trying to do node analysis to find the gain as a function of R3, R4, R5 and not succeeding. :)

Circuit Wiring Diagrams says the gain is 1+(R4/R5) = (R4 + R5)/R5

Radio-Electronics.com says (R4 + R5)/R4.

So I'm confused, but 1+R4/R5 matches my simulations.

And if it doesn't depend on R3, then how do you set R3?
 
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AndrewT

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Joined 2004
You have searched for and found a bad circuit.
It won't drive a 2ohm speaker, properly
2W into 4r0 requires a maximum output of 4Vac and that could be obtained using a supply of 12Vdc, not 24Vdc.
It could be developed into a stage to drive line level signals into a 2k load.
 
J

JoelM81

Member
Joined 2007
AndrewT said:
You have searched for and found a bad circuit.
It won't drive a 2ohm speaker, properly
2W into 4r0 requires a maximum output of 4Vac and that could be obtained using a supply of 12Vdc, not 24Vdc.
It could be developed into a stage to drive line level signals into a 2k load.
Click to expand...

I know it won't drive a speaker. My goal is improved linearity over a common emitter amplifier, and low noise. I was able to work through the analysis and confirm that the AC gain is 1+R4/R5, if beta >> 1.

Some variations are also shown here (but without any explanation), and here (fig 39).
 
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PMA

PMA

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Joined 2002
pmacura.cz/audiopage.html
Paid Member
Stinger said:
Hi everyone,
Would someone please determine the components values for this simple amplifier?



I need to run it with a 24V battery and also the sound quality isn't important at all!

Thank you in advance
Stinger.
Click to expand...

Here we go - you will need a big heatsink!!! :D
 

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