Stability evaluation method using phase response measurements

In almost all linear applications the internally compensated operational amplifiers have no stability problems. But, some particular circuits as “the capacitive load amplifier” or “the composite amplifier” may have ringing step response. The paper proposes a new technique by which the integrated circuit user can estimate the open-loop Bode diagrams of the amplifier configured with a negative feedback loop. The method has three advantages. First, the phase measurements are executed directly on the op-amp application circuit. Second, the application designer can calculate the open-loop transfer function dynamic model, and the amplifier phase margin. Third, if there are stability issues, the circuit designer has information necessary to calculate the op-amp frequency compensation network.