Experimental study on energy injection damage of a GaAs low noise amplifier with and without DC bias

An experimental study on energy injection induced damage by a pulse-modulated carrier with 300 MHz radio frequency (RF) signal source to a GaAs bipolar low noise amplifier (LNA) with and without DC bias is presented in this paper based on the measurement of the noise figure and gain variation of GaAs LNA prior to and after the energy injection. Experimental results show that the noise figures of LNA with DC bias increase obviously but the gain characteristics still retain the normal level after the energy injection. Sample dissection illustrates that the energy injection damages the collector¿s metallization so that the LNA noise increases. However, the gain characteristics of LNA without DC bias lose absolutely and the noise level increases abruptly after the energy injection because of transistors breakdown taking place between the base and the collector. Experiment results show that the noise figure of GaAs LNA is more sensitive to energy injection than gain characteristics, and due to the complexity of the effect of energy injection induced damage, it is insufficient to evaluate the damage using the gain difference as the sole parameter before and after the injection. Experiment results also indicate that the GaAs-LNA without DC bias is easier to cause functional failure of the circuit, but the damage induced even by a higher level energy injection to the GaAs-LNA with a normal DC bias is only a soft defect and does not cause any functional failure of the circuit.