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Rf transistor impedance format

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adnan012

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Hi,
I am confused about the format of input and output impedance of RF transistors. For some devices impedance are given in series form and in parallel form for other devices. Some data sheets do not mention. Why series to parallel or parallel to series transformation is required.

I am using pd85004 ldmos for amplifier. When its model is simulated in ads using LSSP simulation, which impedance format parallel or series it gives?
 

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Usually RF components are characterized by s-parameters, that are neither parallel nor series circuit parameters but can be converted to both, if you need.
 

kspalla

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Basically matching circuit can have multiple methods to match to 50 ohm based on bandwidth.
based on the impedance of the load it is may be simple to use series or shunt. Ultimately whether the matching is meeting in the required band.

I suggest reading matching methods using smith chart.
Regards
 

adnan012

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Thanks for reply.

I want to match PD85004 over the band of 800 to 850 MHz. Previously i was following philips rf application note. But it was difficult to work with it (in UHF range). Kindly suggest me the best solution for matching.
 

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  • ECO7806.pdf
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adnan012

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in ECO7806 the blw32 transistor impedance is tabulated in series for it is then converted to parallel for which is 82 ohm with 4.2pf in parallel. 82 ohm transformed and matched over a wideband using T transformer. i my case the pg85004 or pd20015 have very low optimum load impedances in the desired band which i found is imposible to match using the ECO7806 method.
 

kspalla

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I checked ST website for information on the device at your band and found none. however ADS file is available from ST.
This will help you and use this model and optimize the circuit.
 

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