Your output signal can never go higher than 12 - 10 = 2V

Where do you get those 10 Volts from?

 

Where do you get those 10 Volts from?

Estimate... base voltage will be roughly 1.2/2.2 * 12 = 6.5V
Emitter when then be about 5.8V, giving emitter current of about 1.1 mA.
That's roughly the collector current, giving you RC's drop as 1.1 * 1.2 = 1.3V

I just rounded it for a Vc of 10V but I guess it's actually closer to 11V.

 

thanks for all the replies.i'm goin onto it. Another question is if i'm using an E-cap for all the 3 capacitors. how should i put the polarity? input signal goes to the negative leg or the positive?

thank you.

 

Are you sure the gain is actually decreasing or are you just distorting your waveform?

your input signal is limited to < 44mV... All your plots show significant distortion on the positive peaks (flattened)

yea. all the positive peaks faces distortion. what should i do? decrease the Vb by varying R1 and R2? Can input signal's limit be higher?

thank you.

 

thanks for all the replies.i'm goin onto it. Another question is if i'm using an E-cap for all the 3 capacitors. how should i put the polarity? input signal goes to the negative leg or the positive?

thank you.

All the capacitors care about is the DC signal level. For example, C2 has 6.54V DC on its right and 0V DC on its left.
How should it be polarized?

 

All the capacitors care about is the DC signal level. For example, C2 has 6.54V DC on its right and 0V DC on its left.
How should it be polarized?

so positive leg of C2 should connect to right .Am i right?

 

Yep, that's right!

 

Try simulate this amplifier: