Version 4 SHEET 1 880 772 WIRE 16 -112 -64 -112 WIRE 112 -112 16 -112 WIRE 528 -112 112 -112 WIRE 432 -96 288 -96 WIRE 112 -80 112 -112 WIRE 432 -80 432 -96 WIRE 48 -32 16 -32 WIRE 288 0 288 -32 WIRE 16 16 16 -32 WIRE 64 16 16 16 WIRE 128 16 112 16 WIRE 224 16 208 16 WIRE 528 16 528 -32 WIRE 224 48 224 16 WIRE 64 96 64 16 WIRE 128 96 128 16 WIRE 160 96 128 96 WIRE 288 96 240 96 WIRE 560 96 288 96 WIRE 16 112 16 96 WIRE -144 160 -224 160 WIRE -48 160 -64 160 WIRE -224 176 -224 160 WIRE 112 208 16 208 WIRE 240 208 192 208 WIRE 368 208 240 208 WIRE 480 208 448 208 WIRE 560 208 560 96 WIRE 560 208 480 208 WIRE 608 208 560 208 WIRE 720 208 688 208 WIRE 240 224 240 208 WIRE 240 352 240 304 WIRE 560 352 560 288 WIRE 720 352 720 272 FLAG -224 256 0 FLAG 528 16 0 FLAG 560 352 0 FLAG 720 352 0 FLAG 240 352 0 FLAG 240 208 x FLAG 432 0 0 FLAG 480 288 0 SYMBOL npn -48 112 R0 SYMATTR InstName Q1 SYMATTR Value QBD135-10/PLP SYMBOL pnp 48 16 M180 WINDOW 0 56 36 Left 0 WINDOW 3 48 59 Left 0 SYMATTR InstName Q2 SYMATTR Value TIP2955 SYMBOL res 0 0 R0 SYMATTR InstName R1 SYMATTR Value 10 SYMBOL voltage 528 -128 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 44 Left 0 SYMATTR SpiceLine Rser=0 SYMATTR InstName V1 SYMATTR Value 30 SYMBOL voltage -224 160 R0 WINDOW 3 24 160 Left 0 WINDOW 123 24 132 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value 12 SYMATTR Value2 AC 0 SYMATTR InstName V2 SYMBOL res -48 144 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R2 SYMATTR Value 100 SYMBOL res 544 192 R0 SYMATTR InstName R3 SYMATTR Value 1k SYMBOL res 0 -128 R0 SYMATTR InstName R4 SYMATTR Value 200 SYMBOL cap 128 80 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 10n SYMBOL res 464 192 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5 SYMATTR Value 0.01 SYMBOL cap 704 208 R0 SYMATTR InstName C3 SYMATTR Value 1µ SYMATTR SpiceLine Rser=0 Lser=0 SYMBOL current 240 304 M180 WINDOW 0 24 77 Left 0 WINDOW 3 24 0 Left 0 WINDOW 123 -125 -4 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName Ii1 SYMATTR Value "" SYMATTR Value2 AC {u(prb)} SYMBOL voltage 208 208 M270 WINDOW 0 32 56 VTop 0 WINDOW 3 -32 56 VBottom 0 WINDOW 123 -37 83 VBottom 0 WINDOW 39 -32 56 VBottom 0 SYMATTR InstName Vi1 SYMATTR Value "" SYMATTR Value2 AC {u(-prb)} SYMBOL npn 224 0 R0 SYMATTR InstName Q3 SYMATTR Value 2N3055 SYMBOL res 144 112 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R6 SYMATTR Value 10 SYMBOL res 224 0 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R7 SYMATTR Value 0.01 SYMBOL voltage 432 -96 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 10 SYMBOL schottky 272 -96 R0 SYMATTR InstName D1 SYMATTR Value MBR735 SYMATTR Description Diode SYMATTR Type diode SYMBOL current 480 288 M180 WINDOW 0 24 77 Left 0 WINDOW 3 -35 -46 Left 0 WINDOW 123 -125 -4 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value -0.1 SYMBOL res 592 224 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R8 SYMATTR Value 0.47 TEXT -336 424 Left 0 !.ac oct 40 1k 250Meg TEXT 304 392 Left 0 ;Probe elements added to inject\nsignals to measure the open loop\nresponse from the closed loop system TEXT -936 -120 Left 0 ;Here the open loop gain is determined from the closed loop system[1].\nThe open loop gain can be plotted by plotting the quantity:\n -1/(1-1/(2*(I(Vi1)@1*V(x)@2-V(x)@1*I(Vi1)@2)+V(x)@1+I(Vi1)@2)) \nAlternatively, you add the following line to your plot.defs file:\n.func T.et.al() -1/(1-1/(2*(I(Vi1)@1*V(x)@2-V(x)@1*I(Vi1)@2)+V(x)@1+I(Vi1)@2))\nAnd then plot simply T.et.al()\n \nThis is an improvement over the technique shown in LoopGain.asc \nbecause it (i) accounts for reverse feedback(it doesn't even\nmatter if you reverse the direction of the probe -- you still compute\nthe same open loop response) and (ii) the inserted probe elements\nresult in a smaller, sparser circuit matrix. TEXT -328 384 Left 0 !.step param prb list -1 1 ; set prb=0 to turn off probe