Noise: *Megavolts* in for picovolts out??

R

Robert Baer

Guest
???WHAT???
Below is an exact copy from LTspice:

Version 4
SHEET 1 1220 708
WIRE -256 128 -256 96
WIRE -256 240 -256 208
WIRE -160 -32 -160 -64
WIRE -128 96 -256 96
WIRE -128 96 -128 48
WIRE -96 16 -96 -208
WIRE -96 48 -128 48
WIRE -96 240 -96 208
WIRE -96 256 -96 240
WIRE -96 448 -96 336
WIRE -80 16 -96 16
WIRE -64 240 -96 240
WIRE -64 320 -64 240
WIRE -32 208 -32 128
WIRE -16 208 -32 208
WIRE -16 240 -64 240
WIRE 0 -64 -160 -64
WIRE 0 16 0 -64
WIRE 0 464 0 416
WIRE 16 -208 -96 -208
WIRE 16 160 16 -208
WIRE 16 192 16 160
WIRE 32 16 0 16
WIRE 96 128 -32 128
WIRE 96 224 48 224
WIRE 96 224 96 128
WIRE 96 336 96 224
WIRE 96 416 80 416
WIRE 128 16 112 16
WIRE 128 32 128 16
WIRE 128 128 96 128
WIRE 128 128 128 112
WIRE 144 160 16 160
WIRE 144 240 144 160
WIRE 256 -208 16 -208
WIRE 256 -144 256 -208
WIRE 256 -32 256 -64
WIRE 256 112 256 -32
WIRE 304 -64 304 -144
WIRE 304 0 304 -64
WIRE 304 192 304 160
WIRE 304 288 304 192
WIRE 320 -144 304 -144
WIRE 320 192 304 192
WIRE 336 -64 304 -64
WIRE 336 -32 256 -32
WIRE 336 288 304 288
WIRE 336 320 -64 320
WIRE 368 -80 368 -112
WIRE 368 240 144 240
WIRE 368 272 368 240
WIRE 448 -144 400 -144
WIRE 448 -48 400 -48
WIRE 448 -48 448 -144
WIRE 448 192 400 192
WIRE 448 304 400 304
WIRE 448 304 448 192
WIRE 480 -208 256 -208
WIRE 480 -112 368 -112
WIRE 480 -112 480 -208
WIRE 480 304 448 304
WIRE 480 304 480 144
WIRE 496 -96 496 -128
WIRE 512 -128 496 -128
WIRE 512 -48 448 -48
WIRE 512 144 480 144
WIRE 608 -128 592 -128
WIRE 608 -48 592 -48
WIRE 608 -48 608 -128
WIRE 608 48 608 -48
WIRE 608 144 592 144
WIRE 608 144 608 80
WIRE 608 176 608 144
WIRE 608 288 608 176
WIRE 624 48 608 48
WIRE 624 80 608 80
WIRE 656 -208 480 -208
WIRE 656 32 656 -208
WIRE 688 -48 608 -48
WIRE 688 176 608 176
WIRE 688 288 608 288
WIRE 784 -48 768 -48
WIRE 784 64 688 64
WIRE 784 64 784 -48
WIRE 800 288 768 288
WIRE 800 320 800 288
WIRE 816 -208 656 -208
WIRE 816 176 768 176
WIRE 816 176 816 -208
WIRE 832 -48 784 -48
WIRE 832 64 784 64
WIRE 928 -48 912 -48
WIRE 928 -32 928 -48
WIRE 928 64 912 64
WIRE 928 64 928 32
WIRE 928 176 928 64
WIRE 1008 -208 816 -208
WIRE 1008 96 1008 -208
FLAG -96 448 0
FLAG 16 256 0
FLAG 256 192 0
FLAG 1008 176 0
FLAG 0 544 0
FLAG -160 48 0
FLAG 368 -16 0
FLAG 368 336 0
FLAG 656 96 0
FLAG 800 320 0
FLAG 928 336 0
FLAG 496 -96 0
FLAG -256 240 0
SYMBOL res -112 32 R0
WINDOW 0 36 54 Left 0
WINDOW 3 30 79 Left 0
SYMATTR InstName TR1
SYMATTR Value 18.2K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -112 112 R0
WINDOW 0 -34 45 Left 0
WINDOW 3 -44 74 Left 0
SYMATTR InstName R1
SYMATTR Value 549
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -112 240 R0
WINDOW 0 -41 37 Left 0
WINDOW 3 -55 70 Left 0
SYMATTR InstName PC
SYMATTR Value {PC}
SYMBOL Opamps\\opamp2 16 160 R0
WINDOW 3 -31 131 Left 0
SYMATTR Value AD8605
SYMATTR InstName U1
SYMBOL res 240 -160 R0
WINDOW 0 -64 62 Left 0
WINDOW 3 -99 24 Left 0
SYMATTR InstName RTAA
SYMATTR Value {20K-TA}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 240 96 R0
WINDOW 0 -67 68 Left 0
WINDOW 3 -56 29 Left 0
SYMATTR InstName RTAB
SYMATTR Value {TA}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Misc\\battery 1008 80 R0
WINDOW 0 9 6 Left 0
WINDOW 3 11 -32 Left 0
SYMATTR InstName VBAT
SYMATTR Value 5.0V
SYMBOL res -16 448 R0
WINDOW 0 1 32 Right 0
WINDOW 3 -10 68 Right 0
SYMATTR InstName RM1
SYMATTR Value 1K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 80 320 R0
WINDOW 0 39 39 Left 0
WINDOW 3 34 70 Left 0
SYMATTR InstName TR2A
SYMATTR Value 45.3K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -16 432 R270
WINDOW 0 -20 88 VLeft 0
WINDOW 3 -46 94 VLeft 0
SYMATTR InstName TR2B
SYMATTR Value {TR2}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 128 0 R90
WINDOW 0 -20 39 VRight 0
WINDOW 3 46 38 VRight 0
SYMATTR InstName R92
SYMATTR Value 976K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 16 0 R90
WINDOW 0 -19 36 VRight 0
WINDOW 3 50 26 VRight 0
SYMATTR InstName R91
SYMATTR Value 5Meg
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -144 64 R180
WINDOW 0 78 69 Right 0
WINDOW 3 93 33 Right 0
SYMATTR InstName R93
SYMATTR Value 0.001
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 112 16 R0
SYMATTR InstName R90
SYMATTR Value 7.5K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Opamps\\opamp2 368 -112 R0
WINDOW 3 13 115 Left 0
SYMATTR Value AD8605
SYMATTR InstName U2
SYMBOL Opamps\\opamp2 368 240 R0
WINDOW 3 28 95 Left 0
SYMATTR Value AD8605
SYMATTR InstName U3
SYMBOL res 416 -160 R90
WINDOW 0 -20 39 VRight 0
WINDOW 3 -21 -27 VRight 0
SYMATTR InstName R2
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 416 176 R90
WINDOW 0 -11 10 VRight 0
WINDOW 3 -12 -49 VRight 0
SYMATTR InstName R3
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 288 64 R0
WINDOW 0 36 51 Left 0
WINDOW 3 70 50 Left 0
SYMATTR InstName R4
SYMATTR Value 10K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 288 -16 R0
WINDOW 0 40 62 Left 0
WINDOW 3 77 63 Left 0
SYMATTR InstName R5
SYMATTR Value {250K-SENS}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Opamps\\opamp2 656 0 R0
WINDOW 3 20 104 Left 0
SYMATTR Value AD8605
SYMATTR InstName U4
SYMBOL res 608 128 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R6
SYMATTR Value 20.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 608 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R7
SYMATTR Value 20.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R8
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 160 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R9
SYMATTR Value 200K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 272 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R10
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 928 48 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R11
SYMATTR Value 47.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 928 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 47 VRight 0
SYMATTR InstName R12
SYMATTR Value 4.73K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL polcap 912 -32 R0
SYMATTR InstName C1
SYMATTR Value 10ľF
SYMBOL res 912 160 R0
SYMATTR InstName R13
SYMATTR Value 2.20k
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 912 240 R0
WINDOW 0 1 32 Right 0
WINDOW 3 -10 68 Right 0
SYMATTR InstName RM2
SYMATTR Value 1K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 608 -144 R90
WINDOW 0 -21 74 VRight 0
WINDOW 3 -20 7 VRight 0
SYMATTR InstName R14
SYMATTR Value 200K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL voltage -256 112 R0
SYMATTR InstName V1
SYMATTR Value 1.91V
TEXT -200 -264 Left 0 !.INCLUDE D:\\SPICE\\AD8605.LIB
TEXT -200 -232 Left 0 !.PARAM TA=8.00K TR2=1.25K PC=12.5K SENS=249K
TEXT -200 -296 Left 0 !.OPTIONS OPTS NUMDGT=4 RELTOL=0.0001 ITL1=850
ITL6=850 NOPAGE NOMOD
TEXT -200 -200 Left 0 !;op
TEXT 80 464 Left 0 ;*5K pot
TEXT 720 48 Left 0 ;N016
TEXT 416 -232 Left 0 !.noise V(n016) V1 oct 8 1E-1 1E6
 
"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:erX4e.1846$An2.1439@newsread2.news.pas.earthlink.net...
???WHAT???
Hello Robert,

You shouldn't cry "wolf" if there is no wolf.

Your circuit has wrong DC-operating points for many
of your amplifiers. They have saturated outputs.
So it's no wonder that the results look strange.
Before one tries .AC or .NOISE, it's mandatory to run
a .OP or .DC to see that no output is limited.

After I have fixed your design, the results are as expected.

Best Regards,
Helmut


Version 4
SHEET 1 1220 708
WIRE -256 128 -256 96
WIRE -256 240 -256 208
WIRE -160 -32 -160 -64
WIRE -128 96 -256 96
WIRE -128 96 -128 48
WIRE -96 16 -96 -208
WIRE -96 48 -128 48
WIRE -96 240 -96 208
WIRE -96 256 -96 240
WIRE -96 448 -96 336
WIRE -80 16 -96 16
WIRE -64 240 -96 240
WIRE -64 320 -64 240
WIRE -32 208 -32 128
WIRE -16 208 -32 208
WIRE -16 240 -64 240
WIRE 0 -64 -160 -64
WIRE 0 16 0 -64
WIRE 0 464 0 416
WIRE 16 -208 -96 -208
WIRE 16 160 16 -208
WIRE 16 192 16 160
WIRE 32 16 0 16
WIRE 96 128 -32 128
WIRE 96 224 48 224
WIRE 96 224 96 128
WIRE 96 336 96 224
WIRE 96 416 80 416
WIRE 128 16 112 16
WIRE 128 32 128 16
WIRE 128 128 96 128
WIRE 128 128 128 112
WIRE 144 160 16 160
WIRE 144 240 144 160
WIRE 256 -208 16 -208
WIRE 256 -144 256 -208
WIRE 256 -32 256 -64
WIRE 256 112 256 -32
WIRE 304 -64 304 -144
WIRE 304 0 304 -64
WIRE 304 192 304 160
WIRE 304 288 304 192
WIRE 320 -144 304 -144
WIRE 320 192 304 192
WIRE 336 -64 304 -64
WIRE 336 -32 256 -32
WIRE 336 288 304 288
WIRE 336 320 -64 320
WIRE 368 -80 368 -112
WIRE 368 240 144 240
WIRE 368 272 368 240
WIRE 448 -144 400 -144
WIRE 448 -48 400 -48
WIRE 448 -48 448 -144
WIRE 448 192 400 192
WIRE 448 304 400 304
WIRE 448 304 448 192
WIRE 480 -208 256 -208
WIRE 480 -112 368 -112
WIRE 480 -112 480 -208
WIRE 480 304 448 304
WIRE 480 304 480 144
WIRE 496 -96 496 -128
WIRE 512 -128 496 -128
WIRE 512 -48 448 -48
WIRE 512 144 480 144
WIRE 608 -128 592 -128
WIRE 608 -48 592 -48
WIRE 608 -48 608 -128
WIRE 608 48 608 -48
WIRE 608 144 592 144
WIRE 608 144 608 80
WIRE 608 176 608 144
WIRE 608 288 608 176
WIRE 624 48 608 48
WIRE 624 80 608 80
WIRE 656 -208 480 -208
WIRE 656 32 656 -208
WIRE 688 -48 608 -48
WIRE 688 176 608 176
WIRE 688 288 608 288
WIRE 784 -48 768 -48
WIRE 784 64 688 64
WIRE 784 64 784 -48
WIRE 800 288 768 288
WIRE 800 320 800 288
WIRE 816 -208 656 -208
WIRE 816 176 768 176
WIRE 816 176 816 -208
WIRE 832 -48 784 -48
WIRE 832 64 784 64
WIRE 928 -48 912 -48
WIRE 928 -32 928 -48
WIRE 928 64 912 64
WIRE 928 64 928 32
WIRE 928 176 928 64
WIRE 1008 -208 816 -208
WIRE 1008 96 1008 -208
FLAG -96 448 0
FLAG 16 256 0
FLAG 256 192 0
FLAG 1008 176 0
FLAG 0 544 0
FLAG -160 48 0
FLAG 368 -16 0
FLAG 368 336 0
FLAG 656 96 0
FLAG 800 320 0
FLAG 928 336 0
FLAG 496 -96 0
FLAG -256 240 0
SYMBOL res -112 32 R0
WINDOW 0 36 54 Left 0
WINDOW 3 30 79 Left 0
SYMATTR InstName TR1
SYMATTR Value 18.2K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -112 112 R0
WINDOW 0 -34 45 Left 0
WINDOW 3 -44 74 Left 0
SYMATTR InstName R1
SYMATTR Value 549
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -112 240 R0
WINDOW 0 -41 37 Left 0
WINDOW 3 -55 70 Left 0
SYMATTR InstName PC
SYMATTR Value {PC}
SYMBOL Opamps\\opamp2 16 160 R0
WINDOW 3 -31 131 Left 0
SYMATTR Value AD8605
SYMATTR InstName U1
SYMBOL res 240 -160 R0
WINDOW 0 -64 62 Left 0
WINDOW 3 -99 24 Left 0
SYMATTR InstName RTAA
SYMATTR Value {20K-TA}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 240 96 R0
WINDOW 0 -67 68 Left 0
WINDOW 3 -56 29 Left 0
SYMATTR InstName RTAB
SYMATTR Value {TA}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Misc\\battery 1008 80 R0
WINDOW 0 9 6 Left 0
WINDOW 3 11 -32 Left 0
SYMATTR InstName VBAT
SYMATTR Value 5.0V
SYMBOL res -16 448 R0
WINDOW 0 1 32 Right 0
WINDOW 3 -10 68 Right 0
SYMATTR InstName RM1
SYMATTR Value 1K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 80 320 R0
WINDOW 0 39 39 Left 0
WINDOW 3 34 70 Left 0
SYMATTR InstName TR2A
SYMATTR Value 45.3K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -16 432 R270
WINDOW 0 -20 88 VLeft 0
WINDOW 3 -46 94 VLeft 0
SYMATTR InstName TR2B
SYMATTR Value {TR2}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 128 0 R90
WINDOW 0 -20 39 VRight 0
WINDOW 3 46 38 VRight 0
SYMATTR InstName R92
SYMATTR Value 976K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 16 0 R90
WINDOW 0 -19 36 VRight 0
WINDOW 3 50 26 VRight 0
SYMATTR InstName R91
SYMATTR Value 5Meg
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -144 64 R180
WINDOW 0 78 69 Right 0
WINDOW 3 93 33 Right 0
SYMATTR InstName R93
SYMATTR Value 0.001
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 112 16 R0
SYMATTR InstName R90
SYMATTR Value 7.5K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Opamps\\opamp2 368 -112 R0
WINDOW 3 13 115 Left 0
SYMATTR Value AD8605
SYMATTR InstName U2
SYMBOL Opamps\\opamp2 368 240 R0
WINDOW 3 28 95 Left 0
SYMATTR Value AD8605
SYMATTR InstName U3
SYMBOL res 416 -160 R90
WINDOW 0 -20 39 VRight 0
WINDOW 3 -21 -27 VRight 0
SYMATTR InstName R2
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 416 176 R90
WINDOW 0 -11 10 VRight 0
WINDOW 3 -12 -49 VRight 0
SYMATTR InstName R3
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 288 64 R0
WINDOW 0 36 51 Left 0
WINDOW 3 70 50 Left 0
SYMATTR InstName R4
SYMATTR Value 10K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 288 -16 R0
WINDOW 0 40 62 Left 0
WINDOW 3 77 63 Left 0
SYMATTR InstName R5
SYMATTR Value {250K-SENS}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Opamps\\opamp2 656 0 R0
WINDOW 3 20 104 Left 0
SYMATTR Value AD8605
SYMATTR InstName U4
SYMBOL res 608 128 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R6
SYMATTR Value 20.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 608 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R7
SYMATTR Value 20.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R8
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 160 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R9
SYMATTR Value 200K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 272 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R10
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 928 48 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R11
SYMATTR Value 47.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 928 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 47 VRight 0
SYMATTR InstName R12
SYMATTR Value 4.73K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL polcap 912 -32 R0
SYMATTR InstName C1
SYMATTR Value 10ľF
SYMBOL res 912 160 R0
SYMATTR InstName R13
SYMATTR Value 2.20k
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 912 240 R0
WINDOW 0 1 32 Right 0
WINDOW 3 -10 68 Right 0
SYMATTR InstName RM2
SYMATTR Value 1K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 608 -144 R90
WINDOW 0 -21 74 VRight 0
WINDOW 3 -20 7 VRight 0
SYMATTR InstName R14
SYMATTR Value 200K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL voltage -256 112 R0
WINDOW 123 24 132 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value2 AC 1
SYMATTR InstName V1
SYMATTR Value 2.5
TEXT -200 -264 Left 0 ;.INCLUDE D:\\SPICE\\AD8605.LIB
TEXT 72 -400 Left 0 !.PARAM TA=10.00K TR2=1.25K PC=1G SENS=249K ; new
TEXT -200 -296 Left 0 ;.OPTIONS OPTS NUMDGT=4 RELTOL=0.0001 ITL1=850
TEXT -200 -200 Left 0 !.op
TEXT 80 464 Left 0 ;*5K pot
TEXT 720 48 Left 0 ;N016
TEXT -192 -472 Left 0 !.noise V(n016) V1 oct 8 1E-1 1E6
TEXT -192 -360 Left 0 !.include ad8605.cir
TEXT -192 -400 Left 0 ;.ac dec 100 1 100k
TEXT -192 -432 Left 0 ;.dc V1 2.49 2.51 1m
TEXT 72 -360 Left 0 ;.PARAM TA=8.00K TR2=1.25K PC=12.5K SENS=249K
TEXT 168 -472 Left 0 ;V1 changed to 2.5V, PC set to 1G, TA changed to 10k



SPICE model file ad605.cir:


* AD605.cir
*
* AD8605 SPICE Macro-model
* Typical Values
* 05/02, Ver. 1.0
* SB, ADSiV apps
*
* Copyright 2002 by Analog Devices
*
* Refer to "README.DOC" file for License Statement. Use of this
* model indicates your acceptance of the terms and provisions in
* the License Statement.
*
* Node Assignments
* noninverting input
* | inverting input
* | | positive supply
* | | | negative supply
* | | | | output
* | | | | |
* | | | | |
..SUBCKT AD8605 1 2 99 50 45
*
* INPUT STAGE
*
M1 14 7 8 8 PIX L=1E-6 W=1600E-6
M2 16 2 8 8 PIX L=1E-6 W=1600E-6
M3 17 7 10 10 NIX L=1E-6 W=1600E-6
M4 18 2 10 10 NIX L=1E-6 W=1600E-6
RC5 14 50 4E+3
RC6 16 50 4E+3
RC7 99 17 4E+3
RC8 99 18 4E+3
C1 14 16 0.6E-12
C2 17 18 0.6E-12
I1 99 8 100E-6
I2 10 50 100E-6
V1 99 9 0.3
V2 13 50 0.3
D1 8 9 DX
D2 13 10 DX
EOS 7 1 POLY(3) (22,98) (73,98) (81,98) 10E-6 1 1 1
IOS 1 2 0.05E-12
*
* CMRR 100dB, POLE AT 4.5KHz
*
ECM1 21 98 POLY(2) (1,98) (2,98) 0 0.5 0.5
CCM1 21 22 3.54E-10
RCM1 21 22 100E3
RCM2 22 98 1
*
* PSRR=95dB, ZERO AT 534Hz
*
EPSY 98 72 POLY(1) (99,50) 0 1
CPS3 72 73 5.30E-9
RPS3 72 73 56234
RPS4 73 98 1
*
*
* VOLTAGE NOISE REFERENCE OF 8nV/rt(Hz)
*
VN1 80 98 0
RN1 80 98 16.45E-3
HN 81 98 VN1 7
RN2 81 98 1
*
* INTERNAL VOLTAGE REFERENCE
*
EREF 98 0 POLY(2) (99,0) (50,0) 0 .5 .5
GSY 99 50 (99,50) 48E-6
EVP 97 98 POLY(1) (99,50) -0.6 0.5
EVN 51 98 POLY(1) (50,99) 0.6 0.5
*
* GAIN STAGE
*
G1 98 30 POLY(2) (14,16) (17,18) 0 56.3E-6 56.3E-6
R1 30 98 5.43E8
CF 45 30 9E-12
D3 30 97 DX
D4 51 30 DX
*
* OUTPUT STAGE
*
M5 45 46 99 99 POX L=1E-6 W=1.08E-3
M6 45 47 50 50 NOX L=1E-6 W=1.61E-3
EG1 99 46 POLY(1) (98,30) 0.4644 1
EG2 47 50 POLY(1) (30,98) 0.4394 1
*
* MODELS
*
..MODEL POX PMOS (LEVEL=2,KP=10E-6,VTO=-0.328,LAMBDA=0.01,RD=0)
..MODEL NOX NMOS (LEVEL=2,KP=10E-6,VTO=+0.328,LAMBDA=0.01,RD=0)
..MODEL PIX PMOS
(LEVEL=2,KP=10E-6,VTO=-0.328,LAMBDA=0.01,KF=2.5E-31,AF=1,TOX=100E-3)
..MODEL NIX NMOS
(LEVEL=2,KP=10E-6,VTO=+0.328,LAMBDA=0.01,KF=2.5E-31,AF=1,TOX=100E-3)
..MODEL DX D(IS=1E-14,RS=5)
..ENDS AD8605
*
*$
 
"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:wJG5e.2947$An2.181@newsread2.news.pas.earthlink.net...
Helmut Sennewald wrote:

"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:erX4e.1846$An2.1439@newsread2.news.pas.earthlink.net...

???WHAT???


Hello Robert,

You shouldn't cry "wolf" if there is no wolf.

Your circuit has wrong DC-operating points for many
of your amplifiers. They have saturated outputs.
So it's no wonder that the results look strange.
Before one tries .AC or .NOISE, it's mandatory to run
a .OP or .DC to see that no output is limited.

After I have fixed your design, the results are as expected.

Best Regards,
Helmut


------------ SNIPped for brevity ---------
Sorry about that; the bridge was connected incorrectly.
I fixed that and get about 230mV in for 300uV out; a lot better but
still rather puzzling.
Here is the fix:
Version 4
SHEET 1 1220 708
WIRE -256 128 -256 96

Hello Robert,

Why is there no analysis command in your file?

What are the 230mV? Did you want type 230uV?

By the way, the noise density at the ouput V(N016) is about
230uV at 1/(2pi)Hz.

Your circuit looks really useless after your latest change.
I talk about the connection of resistor RTAA to the input source.
Now the circuit amplifies only a very small fraction of the input.

Still LTspice simulates it correctly. I never believe that
you simulate with LTspice. You would get correct results
with LTspice as I have got.

What simulator do you use?

Best Regards,
Helmut
 
Helmut Sennewald wrote:

"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:wJG5e.2947$An2.181@newsread2.news.pas.earthlink.net...

Helmut Sennewald wrote:


"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:erX4e.1846$An2.1439@newsread2.news.pas.earthlink.net...


???WHAT???


Hello Robert,

You shouldn't cry "wolf" if there is no wolf.

Your circuit has wrong DC-operating points for many
of your amplifiers. They have saturated outputs.
So it's no wonder that the results look strange.
Before one tries .AC or .NOISE, it's mandatory to run
a .OP or .DC to see that no output is limited.

After I have fixed your design, the results are as expected.

Best Regards,
Helmut



------------ SNIPped for brevity ---------
Sorry about that; the bridge was connected incorrectly.
I fixed that and get about 230mV in for 300uV out; a lot better but
still rather puzzling.
Here is the fix:
Version 4
SHEET 1 1220 708
WIRE -256 128 -256 96



Hello Robert,

Why is there no analysis command in your file?

What are the 230mV? Did you want type 230uV?

By the way, the noise density at the ouput V(N016) is about
230uV at 1/(2pi)Hz.

Your circuit looks really useless after your latest change.
I talk about the connection of resistor RTAA to the input source.
Now the circuit amplifies only a very small fraction of the input.

Still LTspice simulates it correctly. I never believe that
you simulate with LTspice. You would get correct results
with LTspice as I have got.

What simulator do you use?

Best Regards,
Helmut


1) The file is from LTspice, and Simulate/Run gives a list of points in
a window. Selecting inoise and/or onoise then results in a graph
covering the frequency range specified in the .noise card.
2) Hope you got the whole file; i see only a few lines above.
3) 40 percent of the bridge drive is not a "very small fraction".
4) If you look carefully, you will note that the bridge is rather close
to balance; a large input signal would thus be attenuated by the bridge.
However, the SENSitivity is at max, near a gain of 21 and the last stage
has a gain of about 5 for an approximate total gain of 105.
I presume that you have guessed that TA (RtaA & RtaB) is a pot with
an adjustable wiper. I did not find any way to put in a Bourns pot of a
given description (one would like a PCB layout to conform to parts).
**
In simulations for DC op points, i have been able to run the bridge
balanced from ground to the 1.91V max and get satisfying results.
Granted that at (or near) ground, the opamps act a little fussy, but
that is to be expected.
 
"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:SU66e.3553$An2.1997@newsread2.news.pas.earthlink.net...
Helmut Sennewald wrote:

"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:wJG5e.2947$An2.181@newsread2.news.pas.earthlink.net...

Helmut Sennewald wrote:


"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:erX4e.1846$An2.1439@newsread2.news.pas.earthlink.net...


???WHAT???


Hello Robert,

You shouldn't cry "wolf" if there is no wolf.

Your circuit has wrong DC-operating points for many
of your amplifiers. They have saturated outputs.
So it's no wonder that the results look strange.
Before one tries .AC or .NOISE, it's mandatory to run
a .OP or .DC to see that no output is limited.

After I have fixed your design, the results are as expected.

Best Regards,
Helmut



------------ SNIPped for brevity ---------
Sorry about that; the bridge was connected incorrectly.
I fixed that and get about 230mV in for 300uV out; a lot better but
still rather puzzling.
Here is the fix:
Version 4
SHEET 1 1220 708
WIRE -256 128 -256 96



Hello Robert,

Why is there no analysis command in your file?

What are the 230mV? Did you want type 230uV?

By the way, the noise density at the ouput V(N016) is about
230uV at 1/(2pi)Hz.

Your circuit looks really useless after your latest change.
I talk about the connection of resistor RTAA to the input source.
Now the circuit amplifies only a very small fraction of the input.

Still LTspice simulates it correctly. I never believe that
you simulate with LTspice. You would get correct results
with LTspice as I have got.

What simulator do you use?

Best Regards,
Helmut
1) The file is from LTspice, and Simulate/Run gives a list of points in a
window. Selecting inoise and/or onoise then results in a graph covering
the frequency range specified in the .noise card.
2) Hope you got the whole file; i see only a few lines above.
3) 40 percent of the bridge drive is not a "very small fraction".
4) If you look carefully, you will note that the bridge is rather close to
balance; a large input signal would thus be attenuated by the bridge.
However, the SENSitivity is at max, near a gain of 21 and the last stage
has a gain of about 5 for an approximate total gain of 105.
I presume that you have guessed that TA (RtaA & RtaB) is a pot with an
adjustable wiper. I did not find any way to put in a Bourns pot of a given
description (one would like a PCB layout to conform to parts).
**
In simulations for DC op points, i have been able to run the bridge
balanced from ground to the 1.91V max and get satisfying results.
Granted that at (or near) ground, the opamps act a little fussy, but
that is to be expected.
Hello Robert,
now it is clear for me what the misunderstanding
between us and the simulation is.

I hadn't realized that the difference signal of your
bridge circuit should be the input for your amplifier,
because your first circuit was different.
Now it's clear why we get the totally misleading high
values for V(inoise). The source supplying the bridge
resistors were specified as the input source.
This bridge has a very high common mode supression and
thus SPICE will calculate a very high V(inoise) to achieve
the calculated V(onoise).
The correction has been very simple. We have to add
a dummy voltage source V2(0V) into one side of the bridge.
After that change, V(inoise) is nearly 1/100 of V(onoise)
as we ever had expected.
Nevertheless, the values calculated by LTspice
have been always mathematically correct.

Best Regards,
Helmut

PS: I have beautyfied your schematic to give it a more
professional look. Ok, I still left these many test
resistors on the left side. Btw, there are examples
for potentiometers in the LTspice user group on Yahoo.
A potentiometer basically is a subcircuit with two
resistors and one parameter(wiper position). The
parameter is passed from the schematic to the subcircuit.


The LTspice schematic test.asc .
Warning, maybe there are splitted lines which have to
be manually corrected. News server often fold lines
longer than e.g. 70 characters. Please keep both files in
the same directory.


Version 4
SHEET 1 1392 708
WIRE -512 -144 -512 -208
WIRE -512 -32 -512 -64
WIRE -384 -208 -512 -208
WIRE -384 -80 -384 -208
WIRE -384 32 -384 0
WIRE -384 240 -384 112
WIRE -384 336 -384 240
WIRE -384 448 -384 416
WIRE -256 240 -384 240
WIRE -176 -112 -208 -112
WIRE -96 240 -176 240
WIRE -96 368 -96 240
WIRE -80 208 -80 112
WIRE -80 528 -80 496
WIRE -80 624 -80 608
WIRE -64 -112 -96 -112
WIRE -64 -64 -64 -112
WIRE -64 48 -64 16
WIRE -64 208 -80 208
WIRE -64 240 -96 240
WIRE -48 496 -80 496
WIRE -32 -112 -64 -112
WIRE -32 192 -32 160
WIRE -32 272 -32 256
WIRE -16 160 -32 160
WIRE 48 224 0 224
WIRE 80 -112 48 -112
WIRE 80 -64 80 -112
WIRE 80 112 -80 112
WIRE 80 112 80 16
WIRE 80 224 48 224
WIRE 80 224 80 112
WIRE 80 400 80 224
WIRE 80 496 32 496
WIRE 80 496 80 480
WIRE 224 -208 -384 -208
WIRE 224 -160 224 -208
WIRE 224 -48 224 -80
WIRE 224 -16 224 -48
WIRE 224 96 224 64
WIRE 384 -80 384 -208
WIRE 384 -16 384 -80
WIRE 384 96 384 64
WIRE 384 208 384 176
WIRE 384 336 384 208
WIRE 432 -208 384 -208
WIRE 432 -80 384 -80
WIRE 432 -48 224 -48
WIRE 432 208 384 208
WIRE 432 336 384 336
WIRE 432 368 -96 368
WIRE 464 -96 464 -128
WIRE 464 -16 464 -32
WIRE 464 320 464 288
WIRE 464 400 464 384
WIRE 480 -128 464 -128
WIRE 480 288 464 288
WIRE 576 -208 512 -208
WIRE 576 -64 496 -64
WIRE 576 -64 576 -208
WIRE 576 208 512 208
WIRE 576 352 496 352
WIRE 576 352 576 208
WIRE 608 -64 576 -64
WIRE 608 208 576 208
WIRE 624 -176 624 -208
WIRE 656 -208 624 -208
WIRE 656 -64 608 -64
WIRE 656 208 608 208
WIRE 768 -208 736 -208
WIRE 768 -64 736 -64
WIRE 768 -64 768 -208
WIRE 768 64 768 -64
WIRE 768 208 736 208
WIRE 768 208 768 96
WIRE 768 320 768 208
WIRE 784 64 768 64
WIRE 784 96 768 96
WIRE 816 48 816 16
WIRE 816 128 816 112
WIRE 816 208 768 208
WIRE 816 320 768 320
WIRE 848 -64 768 -64
WIRE 848 16 816 16
WIRE 928 208 896 208
WIRE 928 320 896 320
WIRE 928 368 928 320
WIRE 960 -64 928 -64
WIRE 960 80 848 80
WIRE 960 80 960 -64
WIRE 1008 -64 960 -64
WIRE 1088 80 960 80
WIRE 1088 80 1088 -32
WIRE 1120 -32 1088 -32
WIRE 1120 80 1088 80
WIRE 1232 -240 1168 -240
WIRE 1232 -224 1232 -240
WIRE 1232 -128 1232 -144
WIRE 1232 -32 1200 -32
WIRE 1232 -16 1232 -32
WIRE 1232 80 1200 80
WIRE 1232 80 1232 48
WIRE 1232 144 1232 80
WIRE 1232 256 1232 224
WIRE 1232 368 1232 336
WIRE 1296 80 1232 80
FLAG -384 448 0
FLAG -32 272 0
FLAG 224 96 0
FLAG 1232 -128 0
FLAG -80 624 0
FLAG -64 48 0
FLAG 464 -16 0
FLAG 464 400 0
FLAG 816 128 0
FLAG 928 368 0
FLAG 1232 368 0
FLAG 624 -176 0
FLAG -512 -32 0
FLAG 1008 -64 o4
IOPIN 1008 -64 Out
FLAG 608 208 o3
FLAG 608 -64 o2
FLAG 48 224 o1
FLAG 1296 80 out
IOPIN 1296 80 Out
FLAG 1168 -240 vcc
IOPIN 1168 -240 Out
FLAG 928 208 vcc
IOPIN 928 208 In
FLAG -16 160 vcc
IOPIN -16 160 In
FLAG 480 288 vcc
IOPIN 480 288 In
FLAG 480 -128 vcc
IOPIN 480 -128 In
FLAG -208 -112 vcc
IOPIN -208 -112 In
FLAG 848 16 vcc
IOPIN 848 16 In
SYMBOL res -400 -96 R0
WINDOW 0 36 54 Left 0
WINDOW 3 30 79 Left 0
SYMATTR InstName TR1
SYMATTR Value 18.2K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -400 16 R0
WINDOW 0 38 41 Left 0
WINDOW 3 38 76 Left 0
SYMATTR InstName R1
SYMATTR Value 549
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -400 320 R0
WINDOW 0 47 48 Left 0
WINDOW 3 37 79 Left 0
SYMATTR InstName PC
SYMATTR Value {PC}
SYMBOL Opamps\\opamp2 -32 160 R0
WINDOW 3 23 92 Left 0
SYMATTR Value AD8605
SYMATTR InstName U1
SYMBOL res 208 -176 R0
WINDOW 0 45 43 Left 0
WINDOW 3 37 92 Left 0
SYMATTR InstName RTAA
SYMATTR Value {20K-TA}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 208 -32 R0
WINDOW 0 42 74 Left 0
WINDOW 3 45 40 Left 0
SYMATTR InstName RTAB
SYMATTR Value {TA}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Misc\\battery 1232 -240 R0
WINDOW 0 9 6 Left 0
WINDOW 3 33 84 Left 0
SYMATTR InstName VBAT
SYMATTR Value 5.0V
SYMBOL res -96 512 R0
WINDOW 0 1 32 Right 0
WINDOW 3 -10 68 Right 0
SYMATTR InstName RM1
SYMATTR Value 1K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 64 384 R0
WINDOW 0 39 39 Left 0
WINDOW 3 34 70 Left 0
SYMATTR InstName TR2A
SYMATTR Value 45.3K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -64 512 R270
WINDOW 0 55 80 VLeft 0
WINDOW 3 -19 80 VLeft 0
SYMATTR InstName TR2B
SYMATTR Value {TR2}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 64 -128 R90
WINDOW 0 -20 39 VRight 0
WINDOW 3 46 38 VRight 0
SYMATTR InstName R92
SYMATTR Value 976K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -80 -128 R90
WINDOW 0 -19 36 VRight 0
WINDOW 3 50 26 VRight 0
SYMATTR InstName R91
SYMATTR Value 5Meg
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -48 32 R180
WINDOW 0 -12 70 Right 0
WINDOW 3 -12 35 Right 0
SYMATTR InstName R93
SYMATTR Value 0.001
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 64 -80 R0
SYMATTR InstName R90
SYMATTR Value 7.5K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Opamps\\opamp2 464 -128 R0
WINDOW 3 17 95 Left 0
SYMATTR Value AD8605
SYMATTR InstName U2
SYMBOL Opamps\\opamp2 464 288 R0
WINDOW 3 26 95 Left 0
SYMATTR Value AD8605
SYMATTR InstName U3
SYMBOL res 528 -224 R90
WINDOW 0 -16 39 VRight 0
WINDOW 3 48 28 VRight 0
SYMATTR InstName R2
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 528 192 R90
WINDOW 0 -17 30 VRight 0
WINDOW 3 48 16 VRight 0
SYMATTR InstName R3
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 368 80 R0
WINDOW 0 33 46 Left 0
WINDOW 3 36 74 Left 0
SYMATTR InstName R4
SYMATTR Value 10K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 368 -32 R0
WINDOW 0 40 62 Left 0
WINDOW 3 41 90 Left 0
SYMATTR InstName R5
SYMATTR Value {250K-SENS}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Opamps\\opamp2 816 16 R0
WINDOW 3 26 94 Left 0
SYMATTR Value AD8605
SYMATTR InstName U4
SYMBOL res 752 192 R90
WINDOW 0 -23 46 VRight 0
WINDOW 3 53 31 VRight 0
SYMATTR InstName R6
SYMATTR Value 20.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 752 -80 R90
WINDOW 0 -17 46 VRight 0
WINDOW 3 53 31 VRight 0
SYMATTR InstName R7
SYMATTR Value 20.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 944 -80 R90
WINDOW 0 -24 44 VRight 0
WINDOW 3 49 34 VRight 0
SYMATTR InstName R8
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 912 192 R90
WINDOW 0 -16 46 VRight 0
WINDOW 3 51 35 VRight 0
SYMATTR InstName R9
SYMATTR Value 200K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 912 304 R90
WINDOW 0 -18 40 VRight 0
WINDOW 3 51 31 VRight 0
SYMATTR InstName R10
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 1216 64 R90
WINDOW 0 -20 44 VRight 0
WINDOW 3 51 33 VRight 0
SYMATTR InstName R11
SYMATTR Value 47.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 1216 -48 R90
WINDOW 0 -18 37 VRight 0
WINDOW 3 53 32 VRight 0
SYMATTR InstName R12
SYMATTR Value 4.73K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL polcap 1216 -16 R0
SYMATTR InstName C1
SYMATTR Value 10ľF
SYMBOL res 1216 128 R0
SYMATTR InstName R13
SYMATTR Value 2.20k
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 1216 240 R0
WINDOW 0 86 33 Right 0
WINDOW 3 70 70 Right 0
SYMATTR InstName RM2
SYMATTR Value 1K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 752 -224 R90
WINDOW 0 -19 36 VRight 0
WINDOW 3 44 32 VRight 0
SYMATTR InstName R14
SYMATTR Value 200K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL voltage -512 -160 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 1.91V
SYMBOL voltage -160 240 R90
WINDOW 0 -32 56 VBottom 0
WINDOW 3 35 85 VTop 0
WINDOW 123 35 38 VTop 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 0
SYMATTR Value2 AC 1
TEXT -392 -392 Left 0 ;.INCLUDE D:\\SPICE\\AD8605.LIB
TEXT -392 -360 Left 0 !.PARAM TA=8.00K TR2=1.25K PC=12.5K SENS=249K
TEXT 96 488 Left 0 ;*5K pot
TEXT -392 -328 Left 0 !;op
TEXT -392 -544 Left 0 !.noise V(o4) V2 oct 50 1E-1 1E6
TEXT -392 -432 Left 0 !.include ad8605.cir
TEXT -392 -472 Left 0 ;.ac dec 100 1 100k
TEXT -392 -504 Left 0 ;.dc V1 1.9 1.92 1m
TEXT -248 160 Left 0 ;INoise
TEXT 992 -104 Left 0 ;ONoise
TEXT -24 -544 Left 0 ;V2 is required for the analysis.
TEXT -504 -232 Left 0 ;Bridge Circuit
LINE Normal 336 160 160 160
LINE Normal 336 -256 336 160
LINE Normal -576 -256 336 -256
LINE Normal -576 16 -576 -256
LINE Normal -448 16 -576 16
LINE Normal -448 512 -448 16
LINE Normal -304 512 -448 512
LINE Normal -304 -176 -304 512
LINE Normal 160 -176 -304 -176
LINE Normal 160 160 160 -176
RECTANGLE Normal -160 304 -272 144
RECTANGLE Normal 1072 -16 976 -128




The model file AD8605.cir.


* AD8605 SPICE Macro-model
* Typical Values
* 05/02, Ver. 1.0
* SB, ADSiV apps
*
* Copyright 2002 by Analog Devices
*
* Refer to "README.DOC" file for License Statement. Use of this
* model indicates your acceptance of the terms and provisions in
* the License Statement.
*
* Node Assignments
* noninverting input
* | inverting input
* | | positive supply
* | | | negative supply
* | | | | output
* | | | | |
* | | | | |
..SUBCKT AD8605 1 2 99 50 45
*
* INPUT STAGE
*
M1 14 7 8 8 PIX L=1E-6 W=1600E-6
M2 16 2 8 8 PIX L=1E-6 W=1600E-6
M3 17 7 10 10 NIX L=1E-6 W=1600E-6
M4 18 2 10 10 NIX L=1E-6 W=1600E-6
RC5 14 50 4E+3
RC6 16 50 4E+3
RC7 99 17 4E+3
RC8 99 18 4E+3
C1 14 16 0.6E-12
C2 17 18 0.6E-12
I1 99 8 100E-6
I2 10 50 100E-6
V1 99 9 0.3
V2 13 50 0.3
D1 8 9 DX
D2 13 10 DX
EOS 7 1 POLY(3) (22,98) (73,98) (81,98) 10E-6 1 1 1
IOS 1 2 0.05E-12
*
* CMRR 100dB, POLE AT 4.5KHz
*
ECM1 21 98 POLY(2) (1,98) (2,98) 0 0.5 0.5
CCM1 21 22 3.54E-10
RCM1 21 22 100E3
RCM2 22 98 1
*
* PSRR=95dB, ZERO AT 534Hz
*
EPSY 98 72 POLY(1) (99,50) 0 1
CPS3 72 73 5.30E-9
RPS3 72 73 56234
RPS4 73 98 1
*
*
* VOLTAGE NOISE REFERENCE OF 8nV/rt(Hz)
*
VN1 80 98 0
RN1 80 98 16.45E-3
HN 81 98 VN1 7
RN2 81 98 1
*
* INTERNAL VOLTAGE REFERENCE
*
EREF 98 0 POLY(2) (99,0) (50,0) 0 .5 .5
GSY 99 50 (99,50) 48E-6
EVP 97 98 POLY(1) (99,50) -0.6 0.5
EVN 51 98 POLY(1) (50,99) 0.6 0.5
*
* GAIN STAGE
*
G1 98 30 POLY(2) (14,16) (17,18) 0 56.3E-6 56.3E-6
R1 30 98 5.43E8
CF 45 30 9E-12
D3 30 97 DX
D4 51 30 DX
*
* OUTPUT STAGE
*
M5 45 46 99 99 POX L=1E-6 W=1.08E-3
M6 45 47 50 50 NOX L=1E-6 W=1.61E-3
EG1 99 46 POLY(1) (98,30) 0.4644 1
EG2 47 50 POLY(1) (30,98) 0.4394 1
*
* MODELS
*
..MODEL POX PMOS (LEVEL=2,KP=10E-6,VTO=-0.328,LAMBDA=0.01,RD=0)
..MODEL NOX NMOS (LEVEL=2,KP=10E-6,VTO=+0.328,LAMBDA=0.01,RD=0)
..MODEL PIX PMOS
(LEVEL=2,KP=10E-6,VTO=-0.328,LAMBDA=0.01,KF=2.5E-31,AF=1,TOX=100E-3)
..MODEL NIX NMOS
(LEVEL=2,KP=10E-6,VTO=+0.328,LAMBDA=0.01,KF=2.5E-31,AF=1,TOX=100E-3)
..MODEL DX D(IS=1E-14,RS=5)
..ENDS AD8605
*
*$
 
Helmut Sennewald wrote:

"Robert Baer" <robertbaer@earthlink.net> schrieb im Newsbeitrag
news:erX4e.1846$An2.1439@newsread2.news.pas.earthlink.net...

???WHAT???


Hello Robert,

You shouldn't cry "wolf" if there is no wolf.

Your circuit has wrong DC-operating points for many
of your amplifiers. They have saturated outputs.
So it's no wonder that the results look strange.
Before one tries .AC or .NOISE, it's mandatory to run
a .OP or .DC to see that no output is limited.

After I have fixed your design, the results are as expected.

Best Regards,
Helmut


------------ SNIPped for brevity ---------
Sorry about that; the bridge was connected incorrectly.
I fixed that and get about 230mV in for 300uV out; a lot better but
still rather puzzling.
Here is the fix:
Version 4
SHEET 1 1220 708
WIRE -256 128 -256 96
WIRE -256 240 -256 208
WIRE -160 -32 -160 -64
WIRE -128 48 -128 -176
WIRE -128 96 -256 96
WIRE -128 96 -128 48
WIRE -96 16 -96 -208
WIRE -96 48 -128 48
WIRE -96 240 -96 208
WIRE -96 256 -96 240
WIRE -96 448 -96 336
WIRE -80 16 -96 16
WIRE -64 240 -96 240
WIRE -64 320 -64 240
WIRE -32 208 -32 128
WIRE -16 208 -32 208
WIRE -16 240 -64 240
WIRE 0 -64 -160 -64
WIRE 0 16 0 -64
WIRE 0 464 0 416
WIRE 16 -208 -96 -208
WIRE 16 160 16 -208
WIRE 16 192 16 160
WIRE 32 16 0 16
WIRE 96 128 -32 128
WIRE 96 224 48 224
WIRE 96 224 96 128
WIRE 96 336 96 224
WIRE 96 416 80 416
WIRE 128 16 112 16
WIRE 128 32 128 16
WIRE 128 128 96 128
WIRE 128 128 128 112
WIRE 144 160 16 160
WIRE 144 240 144 160
WIRE 256 -176 -128 -176
WIRE 256 -144 256 -176
WIRE 256 -32 256 -64
WIRE 256 112 256 -32
WIRE 304 -64 304 -144
WIRE 304 0 304 -64
WIRE 304 192 304 160
WIRE 304 288 304 192
WIRE 320 -144 304 -144
WIRE 320 192 304 192
WIRE 336 -64 304 -64
WIRE 336 -32 256 -32
WIRE 336 288 304 288
WIRE 336 320 -64 320
WIRE 368 -80 368 -112
WIRE 368 240 144 240
WIRE 368 272 368 240
WIRE 448 -144 400 -144
WIRE 448 -48 400 -48
WIRE 448 -48 448 -144
WIRE 448 192 400 192
WIRE 448 304 400 304
WIRE 448 304 448 192
WIRE 480 -208 16 -208
WIRE 480 -112 368 -112
WIRE 480 -112 480 -208
WIRE 480 304 448 304
WIRE 480 304 480 144
WIRE 496 -96 496 -128
WIRE 512 -128 496 -128
WIRE 512 -48 448 -48
WIRE 512 144 480 144
WIRE 608 -128 592 -128
WIRE 608 -48 592 -48
WIRE 608 -48 608 -128
WIRE 608 48 608 -48
WIRE 608 144 592 144
WIRE 608 144 608 80
WIRE 608 176 608 144
WIRE 608 288 608 176
WIRE 624 48 608 48
WIRE 624 80 608 80
WIRE 656 -208 480 -208
WIRE 656 32 656 -208
WIRE 688 -48 608 -48
WIRE 688 176 608 176
WIRE 688 288 608 288
WIRE 784 -48 768 -48
WIRE 784 64 688 64
WIRE 784 64 784 -48
WIRE 800 288 768 288
WIRE 800 320 800 288
WIRE 816 -208 656 -208
WIRE 816 176 768 176
WIRE 816 176 816 -208
WIRE 832 -48 784 -48
WIRE 832 64 784 64
WIRE 928 -48 912 -48
WIRE 928 -32 928 -48
WIRE 928 64 912 64
WIRE 928 64 928 32
WIRE 928 176 928 64
WIRE 1008 -208 816 -208
WIRE 1008 96 1008 -208
FLAG -96 448 0
FLAG 16 256 0
FLAG 256 192 0
FLAG 1008 176 0
FLAG 0 544 0
FLAG -160 48 0
FLAG 368 -16 0
FLAG 368 336 0
FLAG 656 96 0
FLAG 800 320 0
FLAG 928 336 0
FLAG 496 -96 0
FLAG -256 240 0
SYMBOL res -112 32 R0
WINDOW 0 36 54 Left 0
WINDOW 3 30 79 Left 0
SYMATTR InstName TR1
SYMATTR Value 18.2K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -112 112 R0
WINDOW 0 -34 45 Left 0
WINDOW 3 -44 74 Left 0
SYMATTR InstName R1
SYMATTR Value 549
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -112 240 R0
WINDOW 0 -41 37 Left 0
WINDOW 3 -55 70 Left 0
SYMATTR InstName PC
SYMATTR Value {PC}
SYMBOL Opamps\\opamp2 16 160 R0
WINDOW 3 -31 131 Left 0
SYMATTR Value AD8605
SYMATTR InstName U1
SYMBOL res 240 -160 R0
WINDOW 0 -64 62 Left 0
WINDOW 3 -99 24 Left 0
SYMATTR InstName RTAA
SYMATTR Value {20K-TA}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 240 96 R0
WINDOW 0 -67 68 Left 0
WINDOW 3 -56 29 Left 0
SYMATTR InstName RTAB
SYMATTR Value {TA}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Misc\\battery 1008 80 R0
WINDOW 0 9 6 Left 0
WINDOW 3 11 -32 Left 0
SYMATTR InstName VBAT
SYMATTR Value 5.0V
SYMBOL res -16 448 R0
WINDOW 0 1 32 Right 0
WINDOW 3 -10 68 Right 0
SYMATTR InstName RM1
SYMATTR Value 1K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 80 320 R0
WINDOW 0 39 39 Left 0
WINDOW 3 34 70 Left 0
SYMATTR InstName TR2A
SYMATTR Value 45.3K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -16 432 R270
WINDOW 0 -20 88 VLeft 0
WINDOW 3 -46 94 VLeft 0
SYMATTR InstName TR2B
SYMATTR Value {TR2}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 128 0 R90
WINDOW 0 -20 39 VRight 0
WINDOW 3 46 38 VRight 0
SYMATTR InstName R92
SYMATTR Value 976K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 16 0 R90
WINDOW 0 -19 36 VRight 0
WINDOW 3 50 26 VRight 0
SYMATTR InstName R91
SYMATTR Value 5Meg
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res -144 64 R180
WINDOW 0 78 69 Right 0
WINDOW 3 93 33 Right 0
SYMATTR InstName R93
SYMATTR Value 0.001
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 112 16 R0
SYMATTR InstName R90
SYMATTR Value 7.5K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Opamps\\opamp2 368 -112 R0
WINDOW 3 13 115 Left 0
SYMATTR Value AD8605
SYMATTR InstName U2
SYMBOL Opamps\\opamp2 368 240 R0
WINDOW 3 28 95 Left 0
SYMATTR Value AD8605
SYMATTR InstName U3
SYMBOL res 416 -160 R90
WINDOW 0 -20 39 VRight 0
WINDOW 3 -21 -27 VRight 0
SYMATTR InstName R2
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 416 176 R90
WINDOW 0 -11 10 VRight 0
WINDOW 3 -12 -49 VRight 0
SYMATTR InstName R3
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 288 64 R0
WINDOW 0 36 51 Left 0
WINDOW 3 70 50 Left 0
SYMATTR InstName R4
SYMATTR Value 10K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 288 -16 R0
WINDOW 0 40 62 Left 0
WINDOW 3 77 63 Left 0
SYMATTR InstName R5
SYMATTR Value {250K-SENS}
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL Opamps\\opamp2 656 0 R0
WINDOW 3 20 104 Left 0
SYMATTR Value AD8605
SYMATTR InstName U4
SYMBOL res 608 128 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R6
SYMATTR Value 20.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 608 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R7
SYMATTR Value 20.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R8
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 160 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R9
SYMATTR Value 200K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 784 272 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R10
SYMATTR Value 100K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 928 48 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 31 VRight 0
SYMATTR InstName R11
SYMATTR Value 47.0K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 928 -64 R90
WINDOW 0 50 48 VRight 0
WINDOW 3 77 47 VRight 0
SYMATTR InstName R12
SYMATTR Value 4.73K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL polcap 912 -32 R0
SYMATTR InstName C1
SYMATTR Value 10ľF
SYMBOL res 912 160 R0
SYMATTR InstName R13
SYMATTR Value 2.20k
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 912 240 R0
WINDOW 0 1 32 Right 0
WINDOW 3 -10 68 Right 0
SYMATTR InstName RM2
SYMATTR Value 1K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL res 608 -144 R90
WINDOW 0 -21 74 VRight 0
WINDOW 3 -20 7 VRight 0
SYMATTR InstName R14
SYMATTR Value 200K
SYMATTR SpiceLine tol=1 pwr=0.1
SYMBOL voltage -256 112 R0
SYMATTR InstName V1
SYMATTR Value 1.91V
TEXT -200 -264 Left 0 !.INCLUDE D:\\SPICE\\AD8605.LIB
TEXT -200 -232 Left 0 !.PARAM TA=8.00K TR2=1.25K PC=12.5K SENS=249K
TEXT 200 -264 Left 0 !;.PRINT V(N005) V(N012) V(N013) V(N016) I(RM1)
I(RM2) V(N004) V(N009)
TEXT -200 -296 Left 0 !.OPTIONS OPTS NUMDGT=4 RELTOL=0.0001 ITL1=850
ITL6=850 NOPAGE NOMOD
TEXT 80 464 Left 0 ;*5K pot
TEXT 720 48 Left 0 ;N016
TEXT 416 -232 Left 0 !;op
TEXT 104 272 Left 0 ;N005
TEXT 488 312 Left 0 ;N013
TEXT 456 -24 Left 0 ;N012
TEXT 488 -232 Left 0 !.noise V(N016) V1 dec 8 1E-1 1E3
 

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