Over-Temperature Protection by Adaptive Output Power Control

Power amplifier transistors suffer from overheating when they operate under extreme conditions. To prevent destructive breakdown an adaptive output power control concept is proposed that makes use of the detected die temperature to limit the output power once a threshold level is crossed. Output power is limited by reducing the effective power control voltage and thereby avoids opposite actuation of the protection loop and that of the power control loop. For a supply voltage of 3.5 V and a nominal output power of 1.8 W the maximum die temperature is reduced from 147degC to 112degC when the output power is adaptively reduced from 32.1 dBm to 27.7 dBm for a VSWR of 4 and worst case mismatch phase