# BJT Amplifier Circuit Analysis Feedback

I've been reading up on small signal analysis to try and better understand audio amplifier circuit design (end goal a discrete BJT guitar amplifier). I'm attempting to apply the knowledge I've picked up (from Microelectronic circuits - Sedra/Smith) to the following amplifier schematic: Would anyone be able to offer some guidance on whether or not I'm doing the correct analysis?

Assumptions: $$\beta = 100$$ $$V_{A} = 100$$ $$V_{be} = 0.7$$

So: $$(1) = 7mA$$ $$(2) \approx 4.6mA$$

Signal Input Impedance (R IN1): $$r_{\pi} = \frac{\beta \cdot V_{T}}{I_{C}}$$ $$r_{\pi} = \frac{100 \cdot 25mV}{2.3mA} \approx 1087 \Omega$$ $$R_{IN1} = R9 || r_{\pi}$$ $$R_{IN1} = 100k \Omega || 1087 \Omega$$ $$R_{IN1} \approx 1075 \Omega$$

Diff Pair Signal Output Impedance (R OUT1): $$r_{o} = \frac{V_{A}}{I_{C}}$$ $$r_{o} = \frac{100V}{2.6mA}$$ $$r_{o} \approx 38462 \Omega$$ $$R_{OUT1} = r_{o}$$

Gain (Avo): $$A_{vo} = -g_{m} \cdot r_{o}$$ $$A_{vo} = - \frac{I_{C}}{V_{T}} \cdot \frac{V_{A}}{I_{C}} = \frac{V_{A}}{V_{T}}$$ $$A_{vo} = -\frac{100V}{25mA}$$ $$A_{vo} = 4,000 V/V$$