| 摘要 |
In an electrosurgical instrument susceptible to varying load impedance, particularly varying load reactance, a fixed frequency radio frequency generator has an output stage (Q1, Q2, TR2-TR4, C1, VC2, 42) consisting of at least one output power device and, coupled to the power device, an output network with a load-dependent resonant condition. To compensate for variations in the load reactance, the output network has a dynamically variable capacitor (VC2) which maintains the tuning of the network substantially constant. Variation of the capacitor (VC2) is performed by means of a phase comparator and servo device (44) which are responsive to variations in phase difference occurring in the output stage due to load reactance changes. |
