Sto eseguendo una simulazione sull'oscillatore Moog Minimoog modello D in LTSpice. Di seguito è riportato il circuito con i modelli necessari.
La generazione dell'onda quadra e dell'onda triangolare funziona come previsto. Il problema che sto riscontrando è con la ricarica del condensatore C4. La rampa di ricarica non va a 5 V secondo la descrizione schematica originale, ma raggiunge solo ~ 4 V. La descrizione schematica (sezione 2.3) recita:
Senza tensione applicata sulla base del transistor Q3, 5uA sta caricando negativamente la parte inferiore del condensatore C4. Questa rampa è tamponata dallo stadio U6 e Q5 e presentata all'ingresso negativo del comparatore U5. Quando la rampa raggiunge 0 V, il comparatore si innesca e produce un impulso + 10 V che accende il JFET J1 e riporta la parte inferiore del condensatore a 5 V. Beh, almeno in teoria.
Ho verificato lo schema molte volte e verificato che (compresi i modelli utilizzati) sono gli stessi del modello D. Ho anche simulato il circuito con una rampa 5V-0V all'ingresso del buffer U6, e questo produce risultati corretti.
Se qualcuno ha qualche idea del perché ci sia un ~ 1V residuo attraverso il condensatore e se c'è un modo per risolverlo, sarei grato.
FullOscillator.asc
Version 4
SHEET 1 1664 1252
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WINDOW 3 32 56 VTop 2
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WINDOW 3 36 40 Left 2
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SYMATTR Value 100K
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WINDOW 3 32 56 VTop 2
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WINDOW 0 0 32 VBottom 2
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SYMATTR Value 220K
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WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
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SYMATTR SpiceLine tol=1 pwr=0.1
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WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
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SYMATTR Value 1N4148
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SYMATTR InstName R22
SYMATTR Value 2K
SYMATTR SpiceLine tol=1 pwr=0.1
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SYMATTR InstName Q3
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WINDOW 39 0 0 Left 0
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SYMATTR Value 2Meg
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WINDOW 3 32 32 VTop 2
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SYMATTR Value 1N4148
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SYMATTR Value LM393A
SYMBOL cap -1616 -80 R180
WINDOW 0 24 57 Left 2
WINDOW 3 24 8 Left 2
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SYMATTR Value 0.001µ
SYMATTR Description Polarized Capacitor
SYMATTR Type polcap
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WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
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SYMATTR Value 1Meg
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WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
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SYMATTR Value 100
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WINDOW 3 0 32 VBottom 2
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SYMATTR Value 100p
SYMATTR Description Polarized Capacitor
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WINDOW 3 32 32 VTop 2
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SYMATTR Description Polarized Capacitor
SYMATTR Type polcap
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SYMATTR Value TL081
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TEXT 904 232 Left 2 !.tran 0 10ms 0 0.5ms startup
TEXT 904 288 Left 2 !.include TL081.301
TEXT 904 336 Left 2 !.include LM393A.5_1
TEXT 904 392 Left 2 ;.wave "C:\\Users\\Boris\\Desktop\\Sawtooth.wav" 16 44.1k V(saw)\n.wave "C:\\Users\\Boris\\Desktop\\Square.wav" 16 44.1k V(squ)\n.wave "C:\\Users\\Boris\\Desktop\\Bent.wav" 16 44.1k V(bent)
TEXT 912 528 Left 2 !.options cshunt = 1e-13
TEXT 904 480 Left 2 ;.wave "C:\\Users\\Boris\\Desktop\\Triangle.wav" 16 44.1k V(tri)
LM393A.5_1
* LM393A VOLTAGE COMPARATOR "MACROMODEL" SUBCIRCUIT
* CREATED USING PARTS VERSION 4.03 ON 03/07/90 AT 14:17
* REV (N/A)
* CONNECTIONS: NON-INVERTING INPUT
* | INVERTING INPUT
* | | POSITIVE POWER SUPPLY
* | | | NEGATIVE POWER SUPPLY
* | | | | OPEN COLLECTOR OUTPUT
* | | | | |
.SUBCKT LM393A 1 2 3 4 5
*
F1 9 3 V1 1
IEE 3 7 DC 100.0E-6
VI1 21 1 DC .75
VI2 22 2 DC .75
Q1 9 21 7 QIN
Q2 8 22 7 QIN
Q3 9 8 4 QMO
Q4 8 8 4 QMI
.MODEL QIN PNP(IS=800.0E-18 BF=2.000E3)
.MODEL QMI NPN(IS=800.0E-18 BF=1002)
.MODEL QMO NPN(IS=800.0E-18 BF=1000 CJC=1E-15 TR=807.4E-9)
E1 10 4 9 4 1
V1 10 11 DC 0
Q5 5 11 4 QOC
.MODEL QOC NPN(IS=800.0E-18 BF=20.29E3 CJC=1E-15 TF=942.6E-12 TR=543.8E-9)
DP 4 3 DX
RP 3 4 46.3E3
.MODEL DX D(IS=800.0E-18)
*
.ENDS
TL081.301
* TL081 OPERATIONAL AMPLIFIER "MACROMODEL" SUBCIRCUIT
* CREATED USING PARTS RELEASE 4.01 ON 06/16/89 AT 13:08
* (REV N/A) SUPPLY VOLTAGE: +/-15V
* CONNECTIONS: NON-INVERTING INPUT
* | INVERTING INPUT
* | | POSITIVE POWER SUPPLY
* | | | NEGATIVE POWER SUPPLY
* | | | | OUTPUT
* | | | | |
.SUBCKT TL081 1 2 3 4 5
*
C1 11 12 3.498E-12
C2 6 7 15.00E-12
DC 5 53 DX
DE 54 5 DX
DLP 90 91 DX
DLN 92 90 DX
DP 4 3 DX
EGND 99 0 POLY(2) (3,0) (4,0) 0 .5 .5
FB 7 99 POLY(5) VB VC VE VLP VLN 0 4.715E6 -5E6 5E6 5E6 -5E6
GA 6 0 11 12 282.8E-6
GCM 0 6 10 99 8.942E-9
ISS 3 10 DC 195.0E-6
HLIM 90 0 VLIM 1K
J1 11 2 10 JX
J2 12 1 10 JX
R2 6 9 100.0E3
RD1 4 11 3.536E3
RD2 4 12 3.536E3
RO1 8 5 150
RO2 7 99 150
RP 3 4 2.143E3
RSS 10 99 1.026E6
VB 9 0 DC 0
VC 3 53 DC 2.200
VE 54 4 DC 2.200
VLIM 7 8 DC 0
VLP 91 0 DC 25
VLN 0 92 DC 25
.MODEL DX D(IS=800.0E-18)
.MODEL JX PJF(IS=15.00E-12 BETA=270.1E-6 VTO=-1)
.ENDS
