Hello im building a common base amplifier with these requirements: "
Design a CB stage (Fig. 5.82) for a voltage gain of 10 and an input impedance of 50 in order to have the same antenna impedance.
Assume IS = 5 × 10−16 A, VA =∞, β = 100, and VCC = 2.5V."

I did the circuit and it seems to be fine, what do u think? what u would change? the only thing is that i saw that the IC is really temperature dependant, so what u would change? consider that i cant change RE or the impedance of 50 will change ( ic isnt really a requirement )

Thanks for all the suggestions.

 

Rin = re || RE not re + RE, with RE = R4 = 500 Ohm being only 50 Ohm in your schematic. Rin will be ~10 % below 50 Ohm with RE = R4 = 500 Ohm and gm = 20 mS. I don't know if that is acceptable for you. Probably just a glitch but you assumed Vbe = 0.9 V instead of ~0.7 V, which makes the base voltage VB higher than neccessary. Thus gm >> 20 mS, re << 50 Ohm and Gv <> 10.

 

Rin = re || RE not re + RE, with RE = R4 = 500 Ohm being only 50 Ohm in your schematic. Rin will be ~10 % below 50 Ohm with RE = R4 = 500 Ohm and gm = 20 mS. I don't know if that is acceptable for you. Probably just a glitch but you assumed Vbe = 0.9 V instead of ~0.7 V, which makes the base voltage VB higher than neccessary. Thus gm >> 20 mS, re << 50 Ohm and Gv <> 10.

ok, beside that its all good?

 

beside that its all good?

All can only be good after you fix everything ;-).

Try replacing V2 with a 100uA current source to let the plots for "10 x Vin" and "Vout/Vin" show you if Rin and voltage gain are at nominal value.

 

See