what should 'Rbias' & 'bias' be for BGU6102 & BGU6104 for an application down around 75MHz ?

[brucebushey]

I'm familiar with what a bias resistor tied to the output of an RF class A amplifier does -- not familiar with what the NXP MMIC Current Adj't resistor does

in 'AN11090 50 Ohm FM LNA', the Current Adj't resistor is referred to as 'Bias setting' and has a value of 15K
in 'AN11091 High Ohmic FM LNA', the Current Adj't resistor is again referred to as 'Bias setting' and has a value of 43K
in 'AN11735 Maximum RF Input Power BGU6102', the Current Adj't resistor is named 'Rbias' and is 5.9k, while L2 there [which connects between Vsupply & RF_out] is named 'bias' & is 27nH
in 'AN11865 BGU6104 Low Noise Amplifier for ISM / LTE bands', the 'LTE 700 – 930 MHz' BOM shows the Current Adj't resistor is 6.8K & L1 there [which again connects between Vsupply & RF_out] is 270nH

I'm trying to determine what 'Rbias' & 'bias' should be for BGU6102 & BGU6104 for an application down around 75MHz
-- in both ap notes AN11090 & AN11091, this component is a resistor, instead of an inductor
-- fig 2., on pg 12 of the BGU6102's data sheet, shows the graph of the 'Supply current as a function of bias resistor; typical values'
-- is the BGU6102's data sheet fig 2. referring to the 'Rbias' or the 'bias' component value ?
-- can someone there direct me to an ap note that'll help me determine what these values should be for an application down around 75MHz ?

[LPP]

In the world of RF, the therm 'bias' means DC conditions of the circuit (current or voltage). It is applied both to the input and output DC feed networks.

BGU610x MMICs consist of RF bipolar transistor and integrated temperature-stabilized bias circuit. Bias circuit provides DC base current to the RF transistor. Actually, the bias circuit is a kind of a current mirror (for example see Figure 5, http://cache.nxp.com/assets/documents/data/en/application-notes/AN3100.pd). The reference current of the mirror is defined by external bias resistor (in parallel with the internal resistor). This reference current determines the base current of the RF transistor and thus the quiescent current of RF transistor. If the external resistor is not used, the default current is determined by the internal resistor. BGU6102 datasheet Figures 2,3 specify Icc as a function of bias resistor and VCC voltage. From these curves, you can evaluate the value of internal resistor to be about 14k.

Now, Rbias determines input bias current and thus the quiescent current of RF transistor. The quiescent current of the transistor determines it's input/output impedances, maximum power, dynamic range and linearity. At this point, you can apply any RF design guides or simulation CADs for class A amplifiers.  The reffered application notes are provided for different applications of the BGU610x MMIC.

http://www.nxp.com/products/rf/rf-amplifiers-low-medium-power/low-noise-amplifiers-lnas/lnas-for-gen...

Low noise amplifier. Optimum Icc current for minimum noise.
High output power. High Icc.
High linearity. High ICC
High ohmic source/load. Low Icc.

Have a great day,
Pavel
NXP TIC

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