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Mitsubishi RD70HHF1 LDMOS model
Under construction...
The Mitsubishi RD70HHF1 is a high-power LDMOS often used in the final stage of commercial HF radios.
Model for Vdd=12.5 V and Idd= 800 mA
Typical S-parameters for this device can be found on the Mitsubishi web site, for a supply voltage of 12.5 V and a drain current of 800 mA.
Using the extraction method previously described, considering only the S-parameters from 50 MHz to 500 MHz, the following small-signal model parameters are determined:
Rg = 0.650 ohm Rd = 0.347 ohm Rs = 0.0 ohm Lg = 0.462 nH Ld = 0.573 nH Ls = 0.039 nH Cgs = 193 pF Cds = 138 pF Cgd = 9.43 pF gm = 2.22 S gds = 11 mSSo the equivalent small-signal circuit for this LDMOS at 800 mA drain current is the following:
Smith chart with measured vs. model S-parameters:
S-parameters fitting details - fitted region is in white background:
S12 fit seems poor, but this is mainly due to its low value and noisy measured data:
