Transimpedance Amplifier: Silly question that's killing me
Your math seems to work out for me, though you're missing the inversion in the second section.

Try breaking the schematic up into two complete sections, and solve them independently.

\$V_o = I_{PMT} * R_1 = 73,000,000 * 0.000,000,000,15 = 73 * 10^{6} * 150 * 10^{-12} = 0.01095 V\$
at the point you're calling \$V_O\$ (e.g. the output node of U1).

Your second-stage gain is: \$V_{gain} = -\frac{R3}{R2} = -\frac{200k}{2k} = -100\$

your output voltage will be \$0.01095 * -100 = -1.095V\$

Your problem seems to be that you forgot that the inverting amplifier, well, inverts. You need to multiply your output voltage by -1.

Silliness: Wolfram Alpha page for the calculation.



Further verification - I stuck the circuit in the falstad circuit simulator. It's an ideal-circuit simulator, so it's not great for real-world analysis, but you're evaluating this circuit with ideal op-amps anyways, so that's not a problem.



At this point, if you're still getting an answer that is "incorrect" (I assume this is homework), you either have a typo somewhere, or the "correct" answer is actually not correct.