SILICON DIODES IN AVALANCHE PULSE-SHARPENING APPLICATIONS

Silicon diodes operated in an avalanche breakdown mode can be used to reduce, or sharpen, the rise times of driving pulses, Proper operation of a diode in this manner requires the application of a driving pulse with sufficient time rate of change of voltage dV/dt. The rapidly cha nging reverse bias produces an electron-hole plasma of sufficient dens ity that the electric field strength in the n region of a p(+)-n-n(+) structure is significantly reduced and the plasma is essentially trapp ed, In effect, the plasma generation causes the device to transition f rom a high-impedance state to a low-impedance state in a short period of time, and thus acts as a fast closing switch, This paper provides a n overview of this mode of operation, A simplified theory of operation is presented, A comparison is made among the results of numerical mod eling, the theory of operation of the silicon avalanche shaper (SAS) d iode, and the theory of operation of the trapped-plasma avalanche-trig gered transit (TRAPATT) mode of operation of a diode. Based on the res ults of numerical modeling, conclusions are drawn on what factors most greatly affect the performance of avalanche shaper diodes, and one op timized design is provided.