* Z:\home\khalils\Downloads\files\data\raw_asc\Electrometer.asc
* Generated by LTspice 26.0.1 for Windows.
* Old Fashioned Electrometer Using Parametric up Conversion\nThese days you should just use a AD549
* 1nA full scale
* 1A full scale
* 100A full scale
* Add for 1A full scale
* 10A full scale
* Add for 100A, 1mA full scale
* 100pA full scale
* 100pA, 1nA, 10nA, 100nA full scale
* 10nA full scale
* 100nA full scale
* Add for 10A full scale
* 1mA full scale
* A 1% mismatch in J1, J2, J3, J4 capacitiances give a 6mV input offset and a 425mV output offset(4.25pA readout error) at 100pA full scale range.\nQ1, Q2, Q3, Q4 require a low drive impedance lest the gain of the loop inverts at high input currents.
* 10V full scale
* Trim to reduce\nerror to a\nfraction of 1pA
* Library below included based on ModelFile attribute of instance XU1 (C:\users\khalils\AppData\Local\LTspice\lib\sym\OpAmps\LT1001.asy)
A1 N006 0 N010 0 0 N006 N009 0 DFLOP Vhigh=0 Vlow=-5 Trise=10n
D2 N027 N031 1N4148
JQ5 N018 0 N011 2N4416
Q9 +V N019 N021 0 2N3904
R23 N005 N004 200
C9 N036 IN 2.5p
I1 0 IN PULSE(0 1000p 1m 1u 1u 5m 10m)
LT2c 0 N011 50
C18 N035 IN .4p
R13 N036 IN 10Meg
C5 N029 0 .01
LT2a N007 IN 50
LT1c N032 0 100
Q10 -V N031 N030 0 2N3906
C23 N004 0 500p
J3 N012 N007 N012 2N5432
J4 N008 N012 N008 2N5432
R3 N033 IN 100G
V1 +V 0 15
R8 +V N015 1.98K
JQ3 N024 N009 0 2N4416
R24 N004 N003 400
R15 N038 IN 100K
R12 N025 N030 49.9
K1 T1a T1b T1c 1.
C4 N023 N022 .01
C14 OUT IN .04p
R19 N039 IN 10K
C7 0 N011 2n
C1 N033 IN .015p
R22 N006 N005 100
Q8 N019 N016 N015 0 2N3906
R5 N023 0 1K
R21 P001 N025 500
R9 N031 -V 4.22K
V2 -V 0 -15
R14 N037 IN 1Meg
R7 +V N016 2.5K
R1 N002 0 500
Q7 N016 N023 N029 0 2N3904
C16 IN 0 100p
LT3c N002 0 25
R20 N013 N028 100
C10 N037 IN 75p
R10 +V N018 1.2K
LT3b 0 N012 25
R6 N029 -V 4.75K
LT2b IN N008 50
R18 N035 IN 100Meg
LT1a 0 N026 100
J2 N001 N008 N001 2N5432
C17 N034 IN .2p
C21 N013 0 .01
R2 N003 N002 25K
C12 N017 N013 .05 IC=0
C15 OUT N013 25p IC=0
C13 N014 N013 .1 IC=0
C2 0 N002 4n
C8 N026 P001 .1
C3 N020 N013 1000p IC=0
D1 N019 N027 1N4148
Q6 +V N018 N022 0 2N3904
JQ4 N032 N006 0 2N4416
LT1b 0 N024 100
C24 N003 0 250p
R17 N034 IN 1G
K3 T3a T3b T3c 1.
V3 N010 0 pulse(-5 0 0 10n 10n .5u 1u)
C6 N015 0 .01
C22 N005 0 1n
XU1 0 N013 +V -V OUT LT1001 ;pnba In+)In-)V+)V-)OUT
R4 N022 -V 4.99K
C11 N038 IN 100p
R11 N021 N025 49.9
R16 OUT IN 10G
K2 T2a T2b T2c 1.
JQ1 N024 N006 N028 2N4416
C20 0 N026 1n
C19 N039 IN 50p
LT3a N001 0 25
JQ2 N032 N009 N028 2N4416
J1 N007 N001 N007 2N5432
.model D D
.lib C:\users\khalils\AppData\Local\LTspice\lib\cmp\standard.dio
.model NPN NPN
.model PNP PNP
.lib C:\users\khalils\AppData\Local\LTspice\lib\cmp\standard.bjt
.model NJF NJF
.model PJF PJF
.lib C:\users\khalils\AppData\Local\LTspice\lib\cmp\standard.jft
.tran 15m
.lib LTC.lib
.backanno
.end

* LTspice schematic (.asc):
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SYMATTR InstName R11
SYMATTR Value 49.9
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SYMATTR InstName C24
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WINDOW 3 61 46 VCenter 2
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SYMATTR Value 2N5432
SYMBOL cap 192 912 R90
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WINDOW 39 60 32 VTop 2
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SYMBOL cap -368 1056 R0
SYMATTR InstName C5
SYMATTR Value .01
SYMBOL cap -736 1120 R90
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WINDOW 3 32 32 VTop 2
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SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL res -288 544 R0
SYMATTR InstName R7
SYMATTR Value 2.5K
SYMBOL cap 1008 608 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
WINDOW 123 60 32 VTop 2
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SYMATTR Value2 IC=0
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SYMATTR InstName Q6
SYMATTR Value 2N3904
SYMBOL diode -176 832 R0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL cap -432 848 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
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SYMATTR Value 100
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WINDOW 3 61 34 Left 2
SYMATTR InstName Q8
SYMATTR Value 2N3906
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SYMATTR Value 50
SYMATTR Type ind
SYMBOL njf -512 464 M270
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WINDOW 3 61 46 VCenter 2
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SYMATTR Value 2N5432
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SYMBOL voltage 256 576 R0
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WINDOW 3 56 54 Left 2
WINDOW 0 56 24 Left 2
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SYMATTR InstName Q1
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WINDOW 3 32 56 VTop 2
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SYMATTR Value 1Meg
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WINDOW 3 32 32 VTop 2
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WINDOW 3 32 56 VTop 2
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SYMATTR Value 50
SYMATTR Type ind
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SYMATTR Value 100
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WINDOW 3 32 56 VTop 2
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SYMATTR Type ind
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WINDOW 3 32 32 VTop 2
WINDOW 123 60 32 VTop 2
SYMATTR InstName C3
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SYMATTR Value2 IC=0
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WINDOW 3 32 56 VTop 2
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SYMATTR Value PULSE(0 1000p 1m 1u 1u 5m 10m)
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SYMATTR Value 2N5432
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WINDOW 3 32 32 VTop 2
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SYMATTR InstName Q9
SYMATTR Value 2N3904
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WINDOW 3 61 34 Left 2
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SYMATTR Value 2N3906
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WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
WINDOW 123 60 32 VTop 2
SYMATTR InstName C12
SYMATTR Value .05
SYMATTR Value2 IC=0
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WINDOW 3 -32 56 VBottom 2
SYMATTR InstName V3
SYMATTR Value pulse(-5 0 0 10n 10n .5u 1u)
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SYMATTR InstName R5
SYMATTR Value 1K
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WINDOW 3 58 23 Left 2
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SYMATTR Value 1.2K
SYMBOL cap -176 400 M180
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WINDOW 3 24 8 Left 2
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SYMATTR Value 4n
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SYMATTR Type ind
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SYMATTR Value 4.75K
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WINDOW 3 32 56 VTop 2
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SYMATTR Value 50
SYMATTR Type ind
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WINDOW 3 32 32 VTop 2
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SYMATTR Value 2N4416
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SYMATTR Value 49.9
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WINDOW 3 32 56 VTop 2
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SYMATTR Value 500
SYMBOL Digital\\dflop 752 320 M0
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SYMATTR Value Vhigh=0 Vlow=-5
SYMATTR Value2 Trise=10n
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WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
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SYMATTR Value 400
SYMBOL cap -496 1856 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
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SYMATTR Value 75p
SYMBOL Opamps\\LT1001 992 944 R0
WINDOW 3 -40 153 Left 2
SYMATTR InstName U1
SYMBOL ind2 320 1040 M180
WINDOW 0 0 72 Right 2
WINDOW 3 2 38 Right 2
SYMATTR InstName T1a
SYMATTR Value 100
SYMATTR Type ind
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WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
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SYMATTR Value .2p
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SYMATTR InstName R9
SYMATTR Value 4.22K
SYMBOL res -480 1296 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R16
SYMATTR Value 10G
SYMBOL res -720 1680 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R13
SYMATTR Value 10Meg
SYMBOL cap -496 1632 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C18
SYMATTR Value .4p
SYMBOL cap 944 880 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
WINDOW 123 60 32 VTop 2
SYMATTR InstName C15
SYMATTR Value 25p
SYMATTR Value2 IC=0
SYMBOL res -720 1232 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 100G
SYMBOL cap -784 848 M180
WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2
SYMATTR InstName C7
SYMATTR Value 2n
SYMBOL njf -512 352 M270
WINDOW 0 34 48 VCenter 2
WINDOW 3 61 46 VCenter 2
SYMATTR InstName J2
SYMATTR Value 2N5432
SYMBOL res -480 1968 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R19
SYMATTR Value 10K
SYMBOL res -720 1904 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R15
SYMATTR Value 100K
SYMBOL cap -496 1408 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C14
SYMATTR Value .04p
SYMBOL njf -624 816 M270
WINDOW 0 51 48 VTop 2
WINDOW 3 -3 44 VLeft 2
SYMATTR InstName Q5
SYMATTR Value 2N4416
SYMBOL res -480 1520 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R18
SYMATTR Value 100Meg
SYMBOL res -720 1456 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R17
SYMATTR Value 1G
SYMBOL ind2 -352 304 M0
WINDOW 0 2 39 Right 2
WINDOW 3 2 74 Right 2
SYMATTR InstName T3c
SYMATTR Value 25
SYMATTR Type ind
SYMBOL cap -896 528 M90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C16
SYMATTR Value 100p
SYMBOL cap 288 320 R0
SYMATTR InstName C22
SYMATTR Value 1n
SYMBOL njf 528 880 M0
WINDOW 0 39 2 Right 2
WINDOW 3 36 101 Right 2
SYMATTR InstName Q3
SYMATTR Value 2N4416
FLAG 256 688 0
FLAG -272 416 0
FLAG -368 416 0
FLAG 336 1040 0
FLAG 400 992 0
FLAG 464 992 0
FLAG 352 688 0
FLAG 256 576 +V
FLAG 352 576 -V
FLAG 992 960 +V
FLAG 992 1056 -V
FLAG 944 1024 0
FLAG -1200 240 0
FLAG 1280 1008 OUT
FLAG -656 432 0
FLAG -448 368 0
FLAG -160 416 0
FLAG -688 832 0
FLAG -400 976 0
FLAG -352 1136 0
FLAG -48 640 0
FLAG -16 1200 -V
FLAG -16 512 +V
FLAG -768 864 0
FLAG -816 544 0
FLAG -912 240 IN
FLAG 224 1040 0
FLAG 1088 416 0
FLAG 832 480 0
FLAG 864 1088 0
FLAG 304 400 0
FLAG 144 400 0
FLAG -16 400 0
TEXT 792 1392 Left 2 !.tran 15m
TEXT -384 256 Bottom 2 !K3 T3a T3b T3c 1.
TEXT 392 864 Bottom 2 !K1 T1a T1b T1c 1.
TEXT -704 232 Bottom 2 !K2 T2a T2b T2c 1.
TEXT -24 216 Bottom 2 ;Old Fashioned Electrometer Using Parametric up Conversion\nThese days you should just use a AD549
TEXT -536 1368 Center 2 ;1nA full scale
TEXT -768 1640 Center 2 ;1A full scale
TEXT -776 1864 Center 2 ;100A full scale
TEXT 1088 816 Left 2 ;Add for 1A full scale
TEXT -536 1816 Center 2 ;10A full scale
TEXT 1088 624 Left 2 ;Add for 100A, 1mA full scale
TEXT -776 1192 Center 2 ;100pA full scale
TEXT 1088 896 Left 2 ;100pA, 1nA, 10nA, 100nA full scale
TEXT -768 1416 Center 2 ;10nA full scale
TEXT -536 1592 Center 2 ;100nA full scale
TEXT 1088 720 Left 2 ;Add for 10A full scale
TEXT -536 2040 Center 2 ;1mA full scale
TEXT -216 1544 Left 2 ;A 1% mismatch in J1, J2, J3, J4 capacitiances give a 6mV input offset and a 425mV output offset(4.25pA readout error) at 100pA full scale range.\nQ1, Q2, Q3, Q4 require a low drive impedance lest the gain of the loop inverts at high input currents.
TEXT 1184 1008 Bottom 2 ;10V full scale
TEXT 976 1120 Top 2 ;Trim to reduce\nerror to a\nfraction of 1pA