Version 4 SHEET 1 996 840 WIRE -336 -16 -400 -16 WIRE -208 -16 -256 -16 WIRE -32 -16 -208 -16 WIRE 208 -16 -32 -16 WIRE -400 16 -400 -16 WIRE -208 16 -208 -16 WIRE -32 16 -32 -16 WIRE 208 64 208 -16 WIRE -400 128 -400 96 WIRE -208 128 -208 80 WIRE -32 128 -32 96 WIRE 80 128 -32 128 WIRE 160 128 80 128 WIRE -32 176 -32 128 WIRE 80 224 80 128 WIRE 112 224 80 224 WIRE 208 224 208 160 WIRE 208 224 176 224 WIRE 336 224 208 224 WIRE 480 224 400 224 WIRE 592 224 480 224 WIRE 768 224 720 224 WIRE 480 256 480 224 WIRE 592 272 592 224 WIRE -32 288 -32 256 WIRE 720 304 720 224 WIRE 720 304 624 304 WIRE 480 368 480 320 WIRE 592 368 592 336 WIRE -272 416 -304 416 WIRE 208 416 208 224 WIRE -272 480 -272 416 WIRE -272 480 -400 480 WIRE -256 480 -272 480 WIRE -96 480 -192 480 WIRE 16 480 -96 480 WIRE 160 480 16 480 WIRE -400 544 -400 480 WIRE -96 544 -96 480 WIRE 208 544 208 512 WIRE 336 544 208 544 WIRE 16 560 16 480 WIRE 208 576 208 544 WIRE 336 592 336 544 WIRE -400 688 -400 624 WIRE -96 688 -96 624 WIRE 16 688 16 624 WIRE 208 688 208 656 WIRE 336 688 336 656 FLAG -96 688 0 FLAG 16 688 0 FLAG 592 368 0 FLAG -208 128 0 FLAG -32 288 0 FLAG 768 224 Output IOPIN 768 224 Out FLAG -400 688 0 FLAG 336 688 0 FLAG -304 416 input IOPIN -304 416 In FLAG 208 688 0 FLAG -400 128 0 FLAG 480 368 0 SYMBOL njf 160 64 R0 SYMATTR InstName J1 SYMATTR Value 2N5484 SYMBOL njf 160 416 R0 SYMATTR InstName J2 SYMATTR Value 2N5484 SYMBOL cap -192 464 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C0 SYMATTR Value 0.1µF SYMATTR SpiceLine V=100 SYMBOL cap 176 208 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C5 SYMATTR Value 1µ SYMATTR SpiceLine V=16 SYMBOL cap 400 208 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C4 SYMATTR Value 1µ SYMATTR SpiceLine V=100 SYMBOL polcap -224 16 R0 WINDOW 0 66 29 Bottom 0 WINDOW 3 80 65 Bottom 0 SYMATTR InstName C6 SYMATTR Value 100µf SYMATTR SpiceLine V=16 SYMBOL cap 0 560 R0 SYMATTR InstName C1 SYMATTR Value 220p SYMATTR SpiceLine V=100 SYMBOL res -112 528 R0 SYMATTR InstName R1 SYMATTR Value 1MEG SYMATTR SpiceLine tol=1 pwr=.25 SYMBOL res -48 0 R0 SYMATTR InstName R5 SYMATTR Value 1MEG SYMATTR SpiceLine tol=1 pwr=.25 SYMBOL res -48 160 R0 SYMATTR InstName R4 SYMATTR Value 1MEG SYMATTR SpiceLine tol=1 pwr=.25 SYMBOL res -240 -32 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R6 SYMATTR Value 100 SYMATTR SpiceLine tol=1 pwr=.25 SYMBOL Misc\\battery -400 0 R0 WINDOW 0 55 56 Bottom 0 WINDOW 3 47 64 Top 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 9 SYMBOL voltage -400 528 R0 WINDOW 123 21 175 Left 0 WINDOW 39 24 132 Left 0 SYMATTR Value2 AC 1 SYMATTR SpiceLine Rser=10k SYMATTR InstName V2 SYMATTR Value SINE(0 .01 1k) SYMBOL polcap 320 592 R0 SYMATTR InstName C2 SYMATTR Value 47µF SYMATTR SpiceLine V=16 SYMBOL res 192 560 R0 SYMATTR InstName R2 SYMATTR Value {RS} SYMBOL cap 464 256 R0 WINDOW 0 -19 56 Left 0 WINDOW 3 -12 146 Left 0 SYMATTR InstName C3 SYMATTR Value 0.47n SYMBOL Robertugo\\Pote 608 240 M0 SYMATTR InstName U1 SYMATTR Value Rt=22K SYMATTR Value2 Set=1 TEXT -448 256 Left 0 !.tran 10ms TEXT -456 296 Left 0 ;.ac dec 100 1 100k TEXT -456 224 Left 0 !.step param RS list 330 1k 3.3k TEXT -416 -512 Left 0 ;A Novel Two Transistor JFET Preamp With A Self Adjusting Current Source For Highest Gain\n \nThe oldest publication I found(1970): \n http://www.national.com/an/AN/AN-32.pdf\nOthers who used it with some modifications:\n http://kickme.to/fatboost\n http://www.muzique.com/amz/mini.htm\n http://www.geofex.com/Article_Folders/foolwfets/foolwfets.htm\n \nThe simulation shows how the gain is affected by the value of the source resistor R2.\nA low pinch-off-voltage Jfet is needed due to the low supply voltage of 9V.\n \nIdeal Gain = Rload / (R2 + 1/S) with Rload = R3||(rds/2) = R3 \n|| means parallel TEXT 144 768 Left 0 ;Lower corner frequency \nfg = 1 /(2*pi*(R2+(1/S))*C2)\nS = Jfet transconductance TEXT 432 80 Left 0 ;Lowpass\nUpper corner frequency \nfu = 1 /(2*pi*R3*C3) TEXT -104 768 Left 0 ;Input filter TEXT -56 -80 Left 0 ;Self Adjusting Current Source RECTANGLE Normal 640 416 432 176 2 RECTANGLE Normal 304 320 -80 -48 2 RECTANGLE Normal 400 736 144 384 2 RECTANGLE Normal 80 736 -144 432 2