IEEE TRANSACTIONS ON ELECTRON DEVICES January current flowing during the interval to may be considered Then(1)becomes to discharge the junction capacitance, and for the over- driven switching, where ts to, (1) reduces to iR(O=(TR+RC3+ -in(o-I,+rc, die (19) with the boundary condition ro>in(to=i the solution of (26)becomes Q(0=IPT, a constant for t< to 1+ The initial condition is ia(t)=IRo exp L-TR +RC4-6 where Ik is defined as the overdriven peak current which is determined by the external circuit such that t=2.38+BC 1 where t, is defined as the time required for iz to decay as shown in Fig. 7 from IRo to 10 per cent of IRo:i.e The solution of (19) with the initial condition(20) is then given by i( 0.1 Ino. (0=(+12)c(-BC)-2) EXPERIMENTAL RESULTS Various types of diodes were selected for switching time measurement. also, current waveforms during the iRO>IRO, switching transient were analyzed using the set-up shown n Fig. 8. Diodes tested are grouped into four general types: 1) germanium gold bonded, 2)germanium expitaxial 0<<t mesa, 3)silicon planar, and 4)silicon diffused mesa. Fig. 9(a)-9(d) shows typical results of the storage time of the overdriven phase; i.e., t to, we have measurement of each group. I, was varied from 1 ma r(lo=iRo (23)to 20 ma and Ir/In up to 100 It can be seen that each curve shows straight line Substituting (23)into (22)and solving for to, we obtain relationship between t, and In(1 +Ir/Ix), as predicted by( 9). The results also indicate that Tp and TR are very t= rc In(1+e-In(1+ Ro (24) constant over the wide range of I, and Ig, as we have assume Fig. 10(a)-10(b) shows typical switching transient characteristics observed with a sampling scope driving a to=RC In (1+ 分h(+2) (25) X-Y recorder. Fig. 10(a) shows normal switching opera- tion, and Fig 10(b)overdriven switching operation. These For t> to, we have ig Ino and results show very good agreement with the switching characteristics given by(14),(22), and (27) TRiR t o(t AY工树篇 Fig. 7-Current switching characteristics of a diode overdriven in reverse directi Fig. 8--Set-up for diode switching test. Authorized licensed use limited to: IEEE Xplore. Downloaded on December 15, 2008 at 03: 47 from IEEE Xplore. Restrictions apply.12 IEEE TRANSACTION# ON ELECTRON DEVICES January current flowkg during the interval to may be considered Then (1) becomes to discharge the junction capacitance, and for the over￾driven switching, where t < to, (I) reduces to iR(t) = (712 f RCj) + iR diR (26) TF -i~(t) = I, + RC; - diR dt (19) where iR(t> > ix(to) = 1x0 Q(t) = Ip~p = constant for t < to. The initial condition is iR(0) = I; (20) where I; is defined as the overdriven peak current which is determined by the external circuit such that as shown in Fig. 7. then given by The solution of (19) with the initial condition (20) is for iR(t) > IRo t %.e., 0 < t < to. At the end of the overdriven phase; Le., t = to, we have iR(tO) = IZO. (23) Substituting (23) into (22) and solving for to, we obtain to = h%,[ In (1 + 2) - In (I + ?)] (24) or 3- OVER-DRIVEN Fig. 7-Current switching characteristics of a diode overdriven in the reverse direction. with the boundary condition iR(tO) = the solution of (26) becomes and where t, is defined as the time required €or i, to decay from IBo to 10 per cent of IRO; i.e., i(tf) = 0.1 IRO. EXPERIMENTAL RESULTS Various types of diodes were selected for switching time measurement. Also, current waveforms during the switching transient were analyzed using the set-up shown in Fig. 8. Diodes tested are grouped into four general. I types: 1) germanium gold bonded, 2) germanium expitaxial mesa, 3) silicon planar, and 4) silicon diffused mesa. Fig. 9(a)-9(d) shows typical results of the storage time measurement of each group. IF was varied from 1 ma to 20 ma and IF/IR up to 100. It can be seen that each curve shows straight line relationship between t, and In (1 + IF/IR), as predicted by (9). The results also indicate that rF and rR are very constant over the wide range of IF and IE, as we have assumed. Fig. lO(a)-lO(b) shows typical switching transient characteristics observed with a sampling scope driving a X-Y recorder. Fig. 10(a) shows normal switching opera￾tion, and Fig. 10(b) overdriven switching operation. These results show very good agreement with the switching characteristics given by (14), (2.29, and (27). I 2.4 X 1 5M 500n POWER SUPPLY mTT￾PA- ~ S4MPLIUG TRIOGER SCOPE PROBE c yr DIODK 0-50v I m - - x-Y REMRDER Fig. 8-Set-up for diode switching test. Authorized licensed use limited to: IEEE Xplore. Downloaded on December 15, 2008 at 03:47 from IEEE Xplore. Restrictions apply