雪崩三极管串联的纳秒脉冲发生器

Nanosecond pulse generator with avalanche transistors in series

雪崩三极管因其快速性、高重复频率等特点被广泛应用于纳秒脉冲发生器。为了提高输出电压,常采用多管串联Marx电路。采用二极管代替传统多管串联Marx电路中的部分限流电阻以减少能量损耗,加快充电速度,提高重复频率,并分析了主电容和限流电阻对输出脉冲幅值和频率的影响。通过雪崩三极管的单管击穿实验,单个三极管的导通内阻最小约为2.5Ω,多管串联Marx电路中的等效内阻使负载侧的输出电压降低,故采用多路Marx并联电路以提高输出电压幅值。通过改变Marx并联模块数量,研究了电路等效内阻对输出脉冲的影响;通过改变负载电阻值,验证了Marx并联电路在小负载下升压效果更佳。实验结果表明,通过相同的4路Marx并联电路进行放电实验,在50Ω负载侧输出上升沿为3.4ns、幅值为2.5kV、可在15kHz下稳定工作的脉冲。

Avalanche transistors have been widely used in nanosecond pulse generators because of their short rise time, high frequency and other characteristics. In order to increase the output voltage amplitude, Marx circuits based on cascaded swit ches are often used. In this paper, diodes were used to replace some current limiting resistors in traditional Marx circuits based on cascaded switches to reduce the energy loss, to speed up the charging speed, and to increase the repetitive frequency. The influ ences of capacitance and the current limiting resistor on the output voltage amplitude and frequency are analyzed. By testing the breakdown of a single BJT, the minimum on resistance of the single BJT was calculated to be about 2.5 Ω, and the equivalent in ternal resistance of the Marx circuit based on cascaded switches reduced the output voltage amplitude over the load, hence multiple Marx circuits in parallel were used to increase the output voltage amplitude. By changing the number of Marx parallel modules, the influence of the equivalent internal resistance of the circuit on the output pulse was studied. By changing the load resistance, it is verified that the Marx circuit in parallel had a better boosting effect overlow resistance loads. The experiments show that, nan osecond pluses with rise time of 3.4 ns, amplitude of 2.5 kV and repetitive frequency of 15 kHz were obtained over a 50 Ω load with four Marx circuits in parallel.