CE amp gain vs. S parameters??

[namtey]

Hi all

I have a very fundamental problem that I can't figure out. I am designing a Common Emitter amplifier which is to be used at about 150MHz. The S-parameter data I have suggests that if I run the transistor with Vce = 3V and Ic = 10mA, I should get a gain of about 20dB.

But designing a bias network to achieve this Vce and Ic I end up with an Rc/Re ratio of about 1.18. And from what I have read, the gain of a CE amplifier is the negative of this ratio.

So howcome there is this massive difference?

Thanks in advance!

 

[ericgibbs]

hi,
A look at your circuit would help us.
Have you considered the effect on the CE gain when the emitter resistor is bypassed by a suitable capacitor.?