The basic parameters characterizing the burn control with the vertical field in an ignited tokamak are discussed in a zero-dimensional model assuming a single circuit for the vertical field and neglecting passive effects. The behavior of the system is determined by three dimensionless quantities: ξ which includes the effect of the mutual inductance; Ũ , related to the gain of the linear feedback; and A, related to the pressure, to the plasma current, and to the vertical field index. Analysis of the circuit equations and of the transport equation leads to the determination of stability regions in the parameter space. It is shown that the effect of the mutual inductance described by ξ is always relevant in the choice of the parameters for a stable burn. As a practical illustration the results are applied to the INTOR case.