wyattmengy
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Hi guys. I have two questions about power amplifier output matching network:
1. In THIS paper, the author states that "For highpower transistors, the device impedance are usually less than 10 ohms. This presents a difficult impedance matching problem in a 50 ohms environment. It often results in highly complex, narrow band and lossy matching networks." Why? I mean, don't we want the output impedance of a power amplifier to be as small as possible so that most of power is delivered to the load (50ohms)? Why does this impose a problem? Matching with Smith chart, isn't it true that we can match whatever load onto 50ohms as long as the load has real part? Why do we care about if the output impedance of the PA is too small?
2. From time to time, I heard people talking about the efficiency of matching networks. Why do matching networks have efficiency if they consist of only passive components (L'c and C's, or lossless T-lines)?
Thanks a lot!!!
1. In THIS paper, the author states that "For highpower transistors, the device impedance are usually less than 10 ohms. This presents a difficult impedance matching problem in a 50 ohms environment. It often results in highly complex, narrow band and lossy matching networks." Why? I mean, don't we want the output impedance of a power amplifier to be as small as possible so that most of power is delivered to the load (50ohms)? Why does this impose a problem? Matching with Smith chart, isn't it true that we can match whatever load onto 50ohms as long as the load has real part? Why do we care about if the output impedance of the PA is too small?
2. From time to time, I heard people talking about the efficiency of matching networks. Why do matching networks have efficiency if they consist of only passive components (L'c and C's, or lossless T-lines)?
Thanks a lot!!!