Not a 23cm PA . . . Sadly . . . /cont.
So having concluded that correct operation of the bias supply and implementation of thermal compensation is dependent on external and unavailable circuitry, I turned to the MRF20060R data sheet for clues as to how else to control the device. Fortunately, the MRF20060R was conceived as a linear device and the data sheet includes a test circuit with an appropriate yet simple bias supply. Interestingly, the tracks and pads in Area ‘E’ (see photograph on previous page) satisfy Motorola’s bias supply with a surface mount PNP power transistor adjacent to the PA device providing the appropriate thermal feedback . . .
Lucent PA Board, original bias supply
Lucent PA Board, modified bias supply
. . . Q3, BDP9501 provides the obvious P-N voltage as well as the necessary negative thermal compensation. D1, BGY90-40 is a schottky diode and thus adds a (smaller but necessary) further P-N voltage whilst R9 provides some safe degree of control over the final bias voltage . . . See below . . . And it works!