Damage Of Strong Electromagnetic Pulse To Bipolar Transistors And Its Protectio

The electromagnetic pulse(EMP)is one of the main forms of threat to the safety of electronic devices.Strong electromagnetic pulses act on electronic systems,causing damage to electronic systems.Bipolar transistors are one of the important components of electronic systems,and studying the damage effect of strong electromagnetic pulses on bipolar transistors can help strengthen the ability of electronic systems to resist strong electromagnetic pulses.Starting from simulation and pulse injection test,this paper obtains the internal electric field current change and damage threshold of bipolar transistor under strong electromagnetic pulse,designs a low-frequency small-signal amplification circuit and tests it,obtains its damage threshold,analyzes the damage cause,and finally proposes a protection design scheme and conducts protection ability test,and concludes the following:(1)Under the application of 2V bias voltage to the BJT collector,the signal voltage is simulated by injecting from the BJT base,and as the signal voltage injected by the base increases,an avalanche breakdown occurs at the transmit junction,the current density increases rapidly,and the current flows from the base to the emitter to form a large current.When the signal voltage is 6V,the slope of the temperature rise curve can be clearly seen,and when the device temperature reaches 600～800K,the temperature change rises sharply.Using the experimental data for fitting analysis,it can be roughly concluded that when the signal voltage is 7V,the damage time of the bipolar transistor is about 0.06 ns.(2)The tolerance of BJT to strong electromagnetic pulse is mainly related to its own structure and process,PN junction thickness and doping concentration have a decisive effect,BJT in high-frequency square wave experiments,the threshold of the collector injection voltage is higher than the base injection,and the conclusion under the nuclear electromagnetic pulse is the opposite.The analysis shows that emitter injection is more sensitive to voltage,while base injection is more sensitive to pulse duration,PNP transistors are more likely to burn out under similar functions,and the sensitivity of different types of transistors to pulse injection varies greatly.The main reason for the failure of the amplifier circuit is the decrease of the resistance of the BJT junction,the junction resistance is reduced from about two hundred megaohms to several thousand ohms,the capacitance is increased by several nanofarads by several nanofarads,and the main reason for the failure of BJT is the short circuit inside the BJT transistor.(3)For the protection of nuclear electromagnetic pulse and lightning electromagnetic pulse,the combined protection circuit of low-frequency amplification circuit is designed,the combined protection circuit is divided into three stages,the first stage is a gas discharge tube,the second stage is a low-pass filter,and the third stage is a TVS tube,the protection performance of the combined protection circuit is tested by using the lightning impulse voltage platform and the nuclear electromagnetic pulse injection platform,and its residual voltage and residual current under different amplitude currents are obtained,of which the nuclear electromagnetic pulse basically meets the standard requirements of less than 1A peak residual current.The measured combined protection circuit has a protective effect on the lowfrequency amplification circuit under 5k A lightning impulse current.