I am trying to design CE amplifier with a gain of 10. I designed the circuit in spice and it worked fine as shown.



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.




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



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?

 

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.

 

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.

 

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

 

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.

 

Keep in mind that as you reduce R5, the gain also starts to drop. It becomes noticeable when R5 < 10 R3

 

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).

 

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?

 

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

Hi m8,
This is what he posted.
E

 

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.

 

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?

I am using function genrator in the oscilloscope

 

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

 

Your circuit attenuates probably because you wrongly swapped the collector and emitter wires on the ancient 2N2222 transistor.

 

Simulation of 2N2222 common emitter amplifier.