I've been reviewing my electrical theory and I'm having trouble trying to calculate an expression for the voltage gain for these two specific circuits. (Images c and d of the question.png attachment). I already know the answers, however I am unable to derive the same solution. Answers are given with my solution attempt.
Kirchoff's loop law and current junction law.
Voltage gain = Output voltage/Input Voltage
R_s is source resistance, R_L is load resistance.
r_o is amplifier output resistance and r_i is amplifier input resistance.
The Attempt at a Solution
I've attached my solution for b if it's unclear what I am asking. I'm pretty sure I've misunderstood something while working it out but haven't been able to figure out the correct steps. Any help is appreciated.
Edit: Attachments are now there.
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