Simplified traveling wave laser (TWL) amplifier equations are given based on a lumped model. Pulse transfer characteristics for a TWL amplifier are examined theoretically. A new class of integrated optical amplifier with three terminals (OPATT) has been proposed as an optical analog of the electric transistor. Analytical formulas and dynamic properties of an OPATT have been considered. OPATT-based optical integrated circuits, including optical differential amplifiers, comparators, saturable oscillators, and optical logic gates, have been investigated theoretically.