Could some electronics guru please help clarify the following. I am a bit rusty on load pulling. I am currently working on some ideas and testing them with SPICE.
Suppose that a RF transistor( e.g. BFU520) is configured as a single stage RF amplifier, with a simple voltage divider base biasing network, a collector resistor, and DC blocking capacitors at the base and collector. The source resistor is set at 50.0 Ohm, and the load resistor is varied. The RMS input and output power(in Watts) is measured for each value of the variable load resistor. The input signal frequency is set to 500 MHz.
Now suppose that using this configration and SPICE transient analysis, the input power is deliveed to the load when the variable load has a value of 150 Ohm.
Now the questions:
- The output impedance of the transistor is approximately 150 Ohm at 500 MHz. Is this correct ?
2, Is it safe to state that at 500 MHz, the input impedance is 50 Ohm, for the given configuration.
- The BFU520 datasheet provides S parameters, and it is possible to compute the Zin, Zout from S11, S22, S12 and S21. But it is not clear if the supplied S parameters are small signal or large signal. Spice transient analysis is large signal, so is the supplied SPICE device model, so if the supplied S parameters ought to be latge signal, but there is no clear indication.
All hints, suggesyions are welcome. Thanks in advance.