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Old 4th May 2009, 02:07 AM   #1
Stinger is offline Stinger  Iran
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Default Two Transistor Amplifier

Hi everyone,
Would someone please determine the components values for this simple amplifier?

Click the image to open in full size.

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

Thank you in advance
Stinger.
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Old 4th May 2009, 02:33 AM   #2
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Default Re: Two Transistor Amplifier

Quote:
Originally posted by Stinger
I need to run it with a 24V battery and also the sound quality isn't important at all!
That is just too easy.

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Old 4th May 2009, 03:11 AM   #3
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R1=30K
R2=2.4K
R3=500
R4=900
R5=100
C1=100uF
C2=100uF

This circuit will have a gain of 10.
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Old 4th May 2009, 03:18 AM   #4
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Load?
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Old 4th May 2009, 12:29 PM   #5
Stinger is offline Stinger  Iran
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Well, thanks again for the fast replies.

The load is a 2...4 ohms speaker (2W). What should be the transistors?
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Old 27th January 2016, 07:42 PM   #6
JoelM81 is offline JoelM81  United States
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Quote:
Originally Posted by sawreyrw View Post
This circuit will have a gain of 10.
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?

Last edited by JoelM81; 27th January 2016 at 07:55 PM.
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Old 29th January 2016, 09:50 AM   #7
AndrewT is offline AndrewT  Scotland
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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.
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Old 29th January 2016, 11:52 AM   #8
JoelM81 is offline JoelM81  United States
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Quote:
Originally Posted by AndrewT View Post
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.
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).

Last edited by JoelM81; 29th January 2016 at 12:12 PM.
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Old 29th January 2016, 12:02 PM   #9
esgigt is offline esgigt  Netherlands
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Check Nelson Pass's ZEN amplifiers out... they use FET's instead of transistors.
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Old 29th January 2016, 10:08 PM   #10
llwhtt is offline llwhtt  United States
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FETs are NOT transistors?

Craig
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