A method and apparatus for delivery of energy by an electro-surgical instrument to a surgical site is disclosed. The apparatus delivers power to electrodes of an electro-surgical instrument during an operation performed at a surgical site. The apparatus includes a processor and a plurality of power delivery channels. The processor signals the onset of an impedance interval and a heating interval. The processor determines a target value of a control parameter to be delivered to a corresponding one of the electrodes. The plurality of power delivery channels are each coupled to the processor and to a corresponding electrode. Each of the power delivery channels responsive to signaling from the processor transitions between the impedance interval and the heating interval. Each of the power delivery channels measures, during the impedance interval, an impedance associated with a delivery of energy to the surgical site by a corresponding electrode. Each of the power delivery channels, during the heating interval, minimizes a difference between a measured value of a control parameter and the target value of the control parameter determined by the processor, to deliver the energy to the surgical site. In an alternate embodiment of the invention a method for controlling power delivery in an electro-surgical instrument is disclosed. In an alternate embodiment of the invention a method for controlling power delivery in an electro-surgical instrument is disclosed. In an alternate embodiment of the invention a method for controlling power delivery in an electro-surgical instrument is disclosed.