Version 4 SHEET 1 2348 680 WIRE -80 256 -80 224 WIRE -80 352 -80 336 WIRE -48 224 -80 224 WIRE 16 176 16 80 WIRE 32 176 16 176 WIRE 32 224 -48 224 WIRE 112 128 112 112 WIRE 112 288 112 272 WIRE 112 512 112 480 WIRE 176 80 16 80 WIRE 256 80 176 80 WIRE 256 80 256 -16 WIRE 256 224 208 224 WIRE 256 224 256 80 WIRE 272 176 192 176 WIRE 272 224 272 176 WIRE 288 176 288 80 WIRE 288 512 288 480 WIRE 304 176 288 176 WIRE 304 224 272 224 WIRE 384 128 384 112 WIRE 384 288 384 272 WIRE 448 80 288 80 WIRE 512 80 448 80 WIRE 512 80 512 32 WIRE 512 224 480 224 WIRE 512 224 512 80 WIRE 528 176 464 176 WIRE 528 224 528 176 WIRE 544 176 544 80 WIRE 560 176 544 176 WIRE 560 224 528 224 WIRE 640 128 640 112 WIRE 640 288 640 272 WIRE 736 80 544 80 WIRE 736 176 720 176 WIRE 768 80 736 80 WIRE 768 224 736 224 WIRE 768 224 768 80 WIRE 768 288 768 224 WIRE 800 32 512 32 WIRE 800 144 800 32 WIRE 832 -16 256 -16 WIRE 832 16 832 0 WIRE 832 144 800 144 WIRE 832 192 832 160 WIRE 848 288 768 288 WIRE 848 336 848 304 WIRE 912 -16 896 -16 WIRE 912 144 896 144 WIRE 928 -16 912 -16 WIRE 928 288 912 288 WIRE 944 144 912 144 WIRE 960 288 928 288 WIRE 1056 -16 1008 -16 WIRE 1056 144 1024 144 WIRE 1056 144 1056 -16 WIRE 1056 288 1040 288 WIRE 1056 288 1056 144 WIRE 1104 144 1056 144 WIRE 1104 144 1104 -16 WIRE 1104 224 1104 176 WIRE 1136 -16 1104 -16 WIRE 1136 144 1104 144 WIRE 1136 176 1104 176 WIRE 1264 -16 1216 -16 WIRE 1264 128 1264 -16 WIRE 1264 160 1200 160 WIRE 1264 160 1264 128 WIRE 1296 160 1264 160 WIRE 1392 160 1376 160 WIRE 1392 160 1392 48 WIRE 1392 224 1392 192 WIRE 1424 48 1392 48 WIRE 1424 160 1392 160 WIRE 1424 192 1392 192 WIRE 1536 48 1504 48 WIRE 1536 160 1536 48 WIRE 1536 176 1488 176 WIRE 1536 176 1536 160 FLAG -80 352 0 FLAG -48 224 clk FLAG 176 80 Q3 FLAG 736 80 Q1 FLAG 112 288 0 FLAG 384 288 0 FLAG 640 288 0 FLAG 112 112 0 FLAG 384 112 0 FLAG 640 112 0 FLAG 1104 224 0 FLAG 112 512 0 FLAG 288 512 0 FLAG 112 400 Vcc FLAG 1168 128 Vcc FLAG 288 400 Vee FLAG 1168 192 Vee FLAG 1264 128 out1 FLAG 448 80 Q2 FLAG 912 -16 V3 FLAG 912 144 V2 FLAG 928 288 V1 FLAG 832 16 0 FLAG 832 192 0 FLAG 848 336 0 FLAG 1392 224 0 FLAG 1456 144 Vcc FLAG 1456 208 Vee FLAG 1536 160 out SYMBOL Digital\\dflop 112 128 R0 WINDOW 0 27 -18 Left 0 WINDOW 3 0 0 Invisible 0 SYMATTR InstName A1 SYMATTR Value Ref=2.5 SYMATTR Value2 Vhigh=5V; Vlow=0 SYMATTR SpiceLine Td=20n Trise=10n Tfall=10n SYMATTR SpiceLine2 tripdt=5n SYMBOL voltage -80 240 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(5V 0 100n 1n 1n 0.5m 1m 15) SYMATTR InstName V1 SYMBOL Digital\\dflop 384 128 R0 WINDOW 0 29 -19 Left 0 WINDOW 3 0 0 Invisible 0 SYMATTR InstName A2 SYMATTR Value Ref=2.5 SYMATTR Value2 Vhigh=5V; Vlow=0 SYMATTR SpiceLine Td=20n Trise=10n Tfall=10n SYMATTR SpiceLine2 tripdt=5n SYMBOL Digital\\dflop 640 128 R0 WINDOW 0 29 -15 Left 0 WINDOW 3 0 0 Invisible 0 SYMATTR InstName A3 SYMATTR Value Ref=2.5 SYMATTR Value2 Vhigh=5V; Vlow=0 SYMATTR SpiceLine Td=20n Trise=10n Tfall=10n SYMATTR SpiceLine2 tripdt=5n SYMBOL Opamps\\LT1001 1168 96 R0 WINDOW 3 22 138 Left 0 SYMATTR InstName U1 SYMBOL res 1024 -32 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 -28 -20 VTop 0 SYMATTR InstName R3 SYMATTR Value 40k SYMBOL res 1040 128 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 36 44 VTop 0 SYMATTR InstName R2 SYMATTR Value 20k SYMBOL res 1056 272 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 10k SYMBOL res 1232 -32 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R4 SYMATTR Value 10k SYMBOL voltage 112 384 R0 SYMATTR InstName V2 SYMATTR Value 15V SYMBOL voltage 288 384 R0 SYMATTR InstName V3 SYMATTR Value -15V SYMBOL Opamps\\LT1001 1456 112 R0 WINDOW 3 22 138 Left 0 SYMATTR InstName U2 SYMBOL res 1392 144 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5 SYMATTR Value 10k SYMBOL res 1520 32 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R6 SYMATTR Value 5k SYMBOL Digital\\buf1 832 -80 R0 SYMATTR InstName A4 SYMATTR Value2 Vhigh=5 Vlow=0 SYMATTR SpiceLine td=10n SYMBOL Digital\\buf1 832 80 R0 SYMATTR InstName A5 SYMATTR Value2 Vhigh=5 Vlow=0 SYMATTR SpiceLine td=10n SYMBOL Digital\\buf1 848 224 R0 SYMATTR InstName A6 SYMATTR Value2 Vhigh=5 Vlow=0 SYMATTR SpiceLine td=10n TEXT -24 24 Left 0 !.tran 0 15m 0 40u TEXT -32 -296 Left 0 ;The first section (D flip-flop A1, A2, A3) implement a 3 bit asynchronous counter\nEach flip flop works in toggle mode (false output connected with D input) TEXT 640 -376 Left 0 ;Educational 3-bit Digital to analog converter TEXT -32 -200 Left 0 ;The three buffers A4, A5 and A6 have the task to separate the counter's outputs (very poor in current) from the D/A inputs TEXT -32 -144 Left 0 ;The three input inverting adder provides Vout1=-(R4/R3)*V3-(R4/R2)*V2-(R4/R1)*V1\nwhere V1=Q1*Vhigh, V2=Q2*Vhigh, V3=Q3*Vhigh; Vhigh=5V and, of course,Q1, Q2 and Q3 are either 1 either 0. Therefore we have:\nVout1=-Q1*Vhigh-Q2*Vhigh/2-Q3*Vhigh/4= -2Vhigh*(Q1/2+Q2/4+Q3/8) TEXT 584 432 Left 0 ;Vout=-(R6/R5)*Vout1=-Vout1/2=Vhigh*((Q1/2+Q2/4+Q3/8)=Vhigh*N/8=Vfs*N/8 TEXT 584 520 Left 0 ;Voutmin (N=1)=1LSB=Vfs/8=0.625V\nVoutmax (N=7)=Vfs*7/8=4.375V=Vfs-1LSB TEXT 584 472 Left 0 ;Vfs=Vhigh=5V; N=0, 1,2.......7