Help with CE Amplifier design

Thread Starter

AHMADee00

Joined Dec 13, 2023
6
I am trying to design CE amplifier with a gain of 10. I designed the circuit in spice and it worked fine as shown.
Screenshot 2024-03-22 041651.png
1711070273824.png

The Voltage across Re is much greater than Vt so the gain will be approximately Rc/Re.

The problem is that when I implement the circuit in the breadboard it gives unexpected results. This is the circuit using same components values and 2n2222a bjt.

1711071267071.png


The voltage across Re is 500mV and Vce = 7V . but the gain is approximately is 0.

1711071659972.png

This is the measured output for the input signal with 7V Amplitude and 1 kHz frequency.

Does anyone know what is the problem with the circuit?
 

dl324

Joined Mar 30, 2015
17,110
What is the complete part number for the transistor. Technically, 2N2222A should be in a metal can. PN2222A and P2N2222A are in TO-92, but they have different pinouts.

If you swap the collector and emitter, the transistor will have very low current gain.
 

MrChips

Joined Oct 2, 2009
31,072
C1 and C2 are too large. They will create very long time constants.
Change them to 1 or 10μF.
R5 is also too large. 10kΩ is good enough.
R1 and R2 are too large. Try reducing them also.
 

Thread Starter

AHMADee00

Joined Dec 13, 2023
6
What is the complete part number for the transistor. Technically, 2N2222A should be in a metal can. PN2222A and P2N2222A are in TO-92, but they have different pinouts.

If you swap the collector and emitter, the transistor will have very low current gain.
It is 2N2222A-1726 as written in the package
 

MrAl

Joined Jun 17, 2014
11,693
I am trying to design CE amplifier with a gain of 10. I designed the circuit in spice and it worked fine as shown.
View attachment 318096
View attachment 318097

The Voltage across Re is much greater than Vt so the gain will be approximately Rc/Re.

The problem is that when I implement the circuit in the breadboard it gives unexpected results. This is the circuit using same components values and 2n2222a bjt.

View attachment 318100


The voltage across Re is 500mV and Vce = 7V . but the gain is approximately is 0.

View attachment 318101

This is the measured output for the input signal with 7V Amplitude and 1 kHz frequency.

Does anyone know what is the problem with the circuit?
Hello,

For one, the transistor has to be biased harder. Lower R1 to start with.
The caps 1000uf are way too large.
1uf is fine.
The output load resistor is too large also, maybe 10k max for testing, 1k better.
 

dl324

Joined Mar 30, 2015
17,110
It is 2N2222A-1726 as written in the package
Could you post the datasheet and/or manufacturer? Every 2N2222A I've seen was in TO-18. I don't think I have any PN2222A and I don't think I've ever had a P2N2222A (didn't even know they existed until a couple years ago).
 

michael8

Joined Jan 11, 2015
428
input signal with 7V Amplitude and 1 kHz frequency.

Isn't that input signal a bit large? What's the output impedance of the signal source?
 

BobTPH

Joined Jun 5, 2013
9,259
This is the measured output for the input signal with 7V Amplitude and 1 kHz frequency.
How do you expect to get a gain of 10 with 7V input? That would be 70V output. Your amp can, at most, output 10V p-p if everything was perfect.

Also, 7V amplitude is ambiguous, it could be peak, peak-to-peak, or RMS, all of which are different.
 

Thread Starter

AHMADee00

Joined Dec 13, 2023
6
How do you expect to get a gain of 10 with 7V input? That would be 70V output. Your amp can, at most, output 10V p-p if everything was perfect.

Also, 7V amplitude is ambiguous, it could be peak, peak-to-peak, or RMS, all of which are different.
It was 7v one peak. I choose this value because when the value less than 7 there will be no output signal. the circuit works as attenuator
 
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