Opamp DC offset Question
When you run a simulation, in most circumstances, the default starting voltage across a capacitor is 0 volts. This means, that at the instant of beginning the simulation, if 4.5 volts is forced onto one plate of that discharged capacitor by the op-amp output, 4.5 volts is also seen on the other plate. Without a discharge resistor (such as R7), the OUT2 node will remain with an average level of 4.5 volts.