Amplifier Design

Thread Starter

ap30

Joined Aug 7, 2020
10
Last edited by a moderator:

Thread Starter

ap30

Joined Aug 7, 2020
10
Did you even bother to read the requirements?

For example, it says “resistors permitted, no smaller than 220 Ohms.”

Does your attempt abide by this?

Bob
It says says values permitted are anything smaller than 220kohms.
 

DickCappels

Joined Aug 21, 2008
6,640
First thing I would try is reducing the input amplitude. If it meets spec then you're done.

If that doesn't do it, figure out which stages are clipping (they all might be) and adjust the base resistors for each stage to get the maximum undistorted output signal out of each stage.
 

ronsimpson

Joined Oct 7, 2019
1,012
C3 is backwards. Not important in SPICE but is in real life.
How did you set the gain of Q1 and Q2?
RC1, RE1 have low values while R6, R7 are high. I would have reversed that.

Q2 is biased to high. Q3 will have no voltage gain so the collector of Q2 must swing from 2V to 8V. You need to increase R4 until the emitter of Q2 is 1 to 2 volts. Will help the clipping. Fix the clipping at Q2-collector before working on Q3.

You need to work down to 20hz. Check the RC frequency response of C6 and 1k of R4||R5.
Also check RE1 C5, R7 C3, C4 Rload. and maybe C2 and 50k.

R4,5 Q2-Base is that connected? It looks open on out pictures.
 

MrAl

Joined Jun 17, 2014
7,849
View attachment 214315

Can someone build this circuit in multisim for me, or at least tell me the steps to build it. I've never done anything like this before and am completely lost. Thanks for any help.
Why did you start another thread with the same questions?

In the previous thread i told you that you have to learn how to design a one transistor circuit before going to a multi transistor circuit. If you learn how to bias the single transistor and set the gain and input/output impedances then you can design a three transistor circuit much easier.
 

MrAl

Joined Jun 17, 2014
7,849
Hello again,

Just to note, the schematic seems to be missing a connection dot. This would prevent the circuit from simulating properly due to the lack of an important connection.

See attachment. The missing dot location is circled in red.
Note the lines had been thickened to help to see the missing dot, but it is missing in the original drawing also.

Amplifier_ThreeTransistor-2.gif
 
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