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In the following circuit, what would be the single-ended \$A_{cm}\$? I realise that there would be no current through \$R_e\$ in common mode and that this is a CE (Common Emitter). However, I am not sure whether the single-ended \$A_{cm}\$ should be

\$-\alpha\cdot R_{c1}/(r_{e5}+r_{o3})\$

or rather

\$-\alpha\cdot R_{c1}/(r_{e5}+2r_{o3})\$

I'd appreciate some help figuring it out. enter image description here

peripatein
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    The best and proper way to determine the answer is to draw the small signal model and analyse that. – Bimpelrekkie May 08 '17 at 20:13
  • Well, I did that but I am not sure my small signal model is correct. But based on my model I am quite sure the denominator should include $r_{o3}$, and not twice that. Yet again, I am not sure. – peripatein May 08 '17 at 20:21
  • Is it essential to attach my drawing in order to get further assistance? – peripatein May 08 '17 at 20:41
  • Since you know no current flows through Re would it matter if you replaced it with an open circuit for your common mode analysis? – owg60 May 08 '17 at 22:31

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