Version 4
SHEET 1 936 680
WIRE 32 144 -48 144
WIRE 224 144 112 144
WIRE 512 144 432 144
WIRE 704 144 592 144
WIRE -48 208 -48 144
WIRE 224 208 224 144
WIRE 432 208 432 144
WIRE 704 208 704 144
WIRE -48 336 -48 288
WIRE 224 336 224 272
WIRE 224 336 -48 336
WIRE 432 336 432 288
WIRE 704 336 704 272
WIRE 704 336 432 336
WIRE -48 368 -48 336
WIRE 432 368 432 336
FLAG -48 368 0
FLAG 224 144 vz20
FLAG 432 368 0
FLAG 704 144 vz15
FLAG -48 144 V1
SYMBOL voltage -48 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL Misc\\EuropeanResistor 16 160 R270
WINDOW 0 27 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 100
SYMBOL diode 208 272 M180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D1
SYMATTR Value SMBJ20A
SYMATTR Prefix X
SYMBOL Misc\\EuropeanResistor 496 160 R270
WINDOW 0 27 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName R2
SYMATTR Value 100
SYMBOL diode 688 272 M180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D2
SYMATTR Value SMBJ15A
SYMATTR Prefix X
SYMBOL bv 432 192 R0
SYMATTR InstName B1
SYMATTR Value V=V(V1)
TEXT -64 8 Left 2 !.lib Littelfuse_TVS_Diode_SMBJxxxA_A_SPICE.lib
TEXT -64 56 Left 2 !.dc V1 -100 100 1
TEXT -64 -104 Left 2 ;https://www.littelfuse.de/technical-resources/spice-models.aspx#question_5