The second stage converts IOUT1 into a voltage and provides frequency compensation. If IOUT1 flows into the collectorcollector junction of Q2-Q4, the second stage output voltage is driven positive. If IOUT1 flows out of the collector-collector junction of Q2-Q4, the second stage output voltage is driven negative. The second stage is a transresistance amplifier.
The capacitor, Cc, in the second stage provides internal frequency compensation. It causes the gain to role off as the frequency increases. Without Cc, external compensation is required to prevent the op amp from oscillating in most applications.