Hi, this question asks me to sketch the small signal equivalent circuit of this circuit (low frequency):
A CE transistor amplifier in fig 5 uses an NPN transistor with βdc=βac = 300. It operates from a +15v power supply, draws a quiescent collect current of 5mA at Vce of 4v. A 300Ω emitter resistor is bypassed by a 33μF capacitor.
a) Find Rc
I found this Rc = 1.9kΩ
b) Sketch a small signal equivalent circuit for the amplifier of part a) and comment on how the capacitor CE appears to the signal source.

The solutions show:

I drew something similar to this except I had included ro where as this diagram doesn't. In my lecture notes, their low-freq small signal model includes ro so I'm wondering if I'm missing something important in the question, that will justify the removal of ro?

Thanks.

 

If ro >> Rc, then it's justifiable to ignore it.

 

Thank you!