Version 4
SHEET 1 1224 744
WIRE 144 80 144 64
WIRE 48 128 -176 128
WIRE 96 128 48 128
WIRE 256 128 208 128
WIRE 448 128 256 128
WIRE 512 128 448 128
WIRE 448 160 448 128
WIRE 144 192 144 176
WIRE 48 272 48 128
WIRE 112 272 48 272
WIRE 256 272 256 128
WIRE 256 272 192 272
WIRE 448 288 448 240
WIRE 448 320 448 288
WIRE 592 320 592 304
WIRE 592 416 592 400
WIRE 80 432 -32 432
WIRE 320 432 144 432
WIRE 448 432 448 400
WIRE -176 512 -176 128
WIRE -32 512 -32 432
WIRE -32 512 -176 512
WIRE 16 512 -32 512
WIRE 128 512 96 512
WIRE 208 512 192 512
WIRE 320 512 320 432
WIRE 320 512 288 512
WIRE 448 512 448 432
WIRE 448 512 320 512
WIRE -176 544 -176 512
WIRE 448 544 448 512
WIRE -176 640 -176 608
WIRE 448 640 448 608
FLAG 592 416 0
FLAG 592 304 3V3
FLAG -176 640 0
FLAG 448 640 0
FLAG 144 192 0
FLAG 144 64 3V3
FLAG 448 288 x
FLAG 448 432 y
FLAG -176 128 in
FLAG 512 128 out
IOPIN 512 128 Out
SYMBOL ind 0 528 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName Ls
SYMATTR Value 0.079577472
SYMBOL cap 128 528 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 -21 21 VBottom 2
SYMATTR InstName Cs
SYMATTR Value 3.183098862f
SYMBOL res 192 528 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName Rs
SYMATTR Value 50
SYMBOL cap 80 448 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName Cp
SYMATTR Value 4p
SYMBOL voltage 592 304 R0
SYMATTR InstName VB
SYMATTR Value 3.3
SYMBOL cap 432 544 R0
SYMATTR InstName C2
SYMATTR Value {CX}
SYMBOL cap -192 544 R0
SYMATTR InstName C1
SYMATTR Value {CX}
SYMBOL res 432 144 R0
SYMATTR InstName R2
SYMATTR Value 100
SYMBOL res 96 288 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 10Meg
SYMBOL 74HCU04 144 64 R0
SYMATTR InstName U1
SYMBOL voltage 448 304 R0
SYMATTR InstName VL
SYMATTR Value AC 1
TEXT 152 616 Left 2 ;Q=100000
TEXT -184 -376 Left 2 !.ac lin 10001 9.999meg 10.001Meg
TEXT -184 -256 Left 2 !* MEASURE frequency @phi = 0°\n.options numdgt=12\n.options measdgt=12\n.options meascplxfmt=polar\n.meas f0 find freq when im(V(x)/V(y))=0\n.meas gain  find mag(V(x)/V(y)) when freq=f0
TEXT -56 -576 Left 2 ;LOOPGAIN SIMULATION OF AN OSCILLATOR
TEXT 384 -512 Left 2 ;fs = 1/(2*pi*sqrt(L*C))\nC=1/(2*pi*fs*Q*Rs)\nL = C*(Q*Rs)^2\nfs=10Meg Rs=50 Q=100000\nC=3.183098862f \nL= 0.079577472
TEXT -40 616 Left 2 ;fs=10MegHz
TEXT -184 -512 Left 2 ;Plot V(x)/V(y)\nThe oscillator frequency will be at phi=0°.\nResults from .MEASURE are in the log-file.\nView -> SPICE Error Log
TEXT -184 -24 Left 2 ;The model of the HCU04 is from Jim.  http://www.analog-innovations.com/
TEXT -184 -312 Left 2 ;.step param CX 10p 30p 1p
TEXT -184 -344 Left 2 !.param CX=22p
TEXT 368 -216 Left 2 ;.tran 0 10m 8m 1n startup
TEXT 368 -184 Left 2 !.options plotwinsize=0
TEXT 368 -248 Left 2 !.options reltol=1e-5
RECTANGLE Normal 368 656 -80 368 2
RECTANGLE Normal 656 -144 352 -288 2
RECTANGLE Normal 208 -288 -208 -400 2