Biasing MSA Series RF Integrated Circuits - App Note

Like discrete transistors, the MSA Series of RF Integrated Circuits can be operated at different bias points to achieve different performance results. These Monolithic Silicon Amplifiers have an internal structure consisting of a Darlington connected pair of bipolar transistors embedded in a matrix of resistors. Since this structure is current controlled, the bias point of an MSA can best be described by specifying the total device current, Id. Both power and gain can be adjusted by varying Id. Curves of typical performance as a function of bias are shown on the individual MSA data sheets. Table 1 lists the range of bias currents over which the various MSAs can be expected to operate. The column labeled "Minimum Recommended Operation" represents the lowest level at which Avago recommends operating the MSA. Operation of the MSA below this threshold causes the IC to be partially turned off; performance becomes unpredictable, and stability problems can result when the device is operated over temperature. There is no intrinsic reliability problem associated with operation below this bias level, however. The column labeled "Guaranteed Performance" lists the bias level at which Avago specifies and tests device performance. It represents a "typical" operating bias point. The "Maximum Recommended Operation" column lists Avago's recommendation for the highest level of bias for the MSA.