| 摘要 |
A broadband power amplifier using a novel high power feedback structure is disclosed in this patent. Feedback is widely used in amplifier design to broaden the bandwidth of the amplifier. Traditionally, the feedback resistor is either an axial resistor placed over the top of the transistor or a surface mount resistor with a long PCB trace making up the rest of the feedback path. However, each of these methods has it's limitations. The axial resistor doesn't have good heat sinking capability and therefore cannot handle high power. The feedback on PCB makes the feedback path long and becomes positive feedback at high frequency, thus limiting the high end frequency of operation of the amplifier in a stable region. The feedback structure disclosed in this patent has a good heat sinking path, has very short feedback path; allowing for higher frequency operation. We successfully applied the feedback structures to a Gallium Nitride (GaN) transistor, which is a new type of power transistor that has low parasitic capacitance and high optimum load impedance, and demonstrated an amplifier with very high output power over extraordinarily broad bandwidth. Matching networks have been optimized to improve performance and stability. We have demonstrated that unconditional stability is achievable while operating over a broad bandwidth using this feedback structure. |
