Learning SPICE

.gitignore

output.txt

circuit.sp

LED adjustment

.PARAM Tstep = 50us
.PARAM Nsteps = 100
.TRAN {Tstep} {Nsteps * Tstep} {Tstep} uic
.PLOT TRAN I(Vled)
.PLOT TRAN V(vfb)
.OPTIONS NOPAGE LIST

* How much light from LED reaches photo diode
.PARAM Rfb = 0.05
* Limits of our LED
.PARAM Iledmax = 20mA
.PARAM Iledmin = 5mA
* Coefficient from LT1932's datasheet
.PARAM K = 225
* Voltage on Rset according to LT1932's datasheet
.PARAM Vrsetdc = 100mV
* Our battery
.PARAM Vmax = 3V
* What signal we want to get
.PARAM Vtarget = 2V
.PARAM Itarget = 20uA
* Transimpedance of the photo diode amplifier
.PARAM Rprobe = {Vtarget / Itarget}
* Tolerable current loss
.PARAM Iloss = {Iledmax / K}
* Estimation of the B-E potential
.PARAM Vcutin = 600mV
* Unity-gain frequency of OA1NP
.PARAM Fu = 8kHz

Vbattery vcc gnd DC {Vmax}

* Light goes to a photo diode
Hlight optin gnd Vled {Rfb}
Xphoto optin gnd pcath gnd BPW34
* Converting the photo diode's current into voltage
Cprobe pcath vfb {K / (2 * 3.14 * Fu * Rprobe)}
Rprobe pcath vfb {Rprobe}
Xopamp gnd pcath vcc gnd vfb OA1NP
* Error amplifier to get the target voltage
R1 vfb r1 {(Vtarget - Vcutin) / Iloss}
R2 gnd r1 {Vcutin / Iloss}
Vb r1 nb1 DC 0V
Q1 r3 nb1 gnd 2N2222A
R3 vcc r3 {Vcutin / Iloss}
Q2 vdc r3 vcc 2N2907A
* LT1932 setup according to its datasheet
Radj vdc rset {K * (Vmax - Vrsetdc) / (Iledmax - Iledmin)}
Rset gnd rset {K * Vrsetdc / Iledmax}
Xdrv rset vcc vcc vcc led LT1932
* LED with an ammeter
Dled vcc lcath LS_L296_typ_T
Vled lcath led DC 0V

.LIB library.sp myOA1NP
.LIB library.sp myLT1932
.LIB library.sp 2N2222A
.LIB library.sp 2N2907A
.LIB library.sp LS_L296
.LIB library.sp BPW34
.END

library.sp

.LIB myOA1NP
.SUBCKT OA1NP in+ in- v+ v- out
.PARAM Gain = 1e6
.PARAM Fu = 8kHz
.PARAM Rp = 1Meg

Egain amp gnd in+ in- {Gain}
Rp amp p {Rp}
Cp p gnd {Gain / (2 * 3.14 * Fu * Rp)}

Bbuf out gnd V = min(max(V(p), V(v-)), V(v+))
.ENDS OA1NP
.ENDL myOA1NP

.LIB myLT1932
.SUBCKT LT1932 rset en vin sw led
.PARAM Vrsetdc = 100mV
.PARAM K = 225

Vrsetdc vrsetdc gnd DC {Vrsetdc}
Vrset vrsetdc rset DC 0V
Fled led gnd Vrset {K}
.ENDS LT1932
.ENDL myLT1932

.LIB 2N2222A
.MODEL 2n2222a npn
+IS=3.88184e-14 BF=929.846 NF=1.10496 VAF=16.5003
+IKF=0.019539 ISE=1.0168e-11 NE=1.94752 BR=48.4545
+NR=1.07004 VAR=40.538 IKR=0.19539 ISC=1.0168e-11
+NC=4 RB=0.1 IRB=0.1 RBM=0.1
+RE=0.0001 RC=0.426673 XTB=0.1 XTI=1
+EG=1.05 CJE=2.23677e-11 VJE=0.582701 MJE=0.63466
+TF=4.06711e-10 XTF=3.92912 VTF=17712.6 ITF=0.4334
+CJC=2.23943e-11 VJC=0.576146 MJC=0.632796 XCJC=1
+FC=0.170253 CJS=0 VJS=0.75 MJS=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
.ENDL 2N2907A

.LIB 2N2907A
.MODEL 2n2907a pnp
+IS=3.02341e-12 BF=523.064 NF=1.16335 VAF=44.2994
+IKF=0.591421 ISE=3.31443e-11 NE=1.9954 BR=4.8572
+NR=1.18959 VAR=1.33092 IKR=5.91421 ISC=3.31443e-11
+NC=3.81262 RB=2.76209 IRB=0.1 RBM=0.880912
+RE=0.0001 RC=0.857407 XTB=0.119647 XTI=1
+EG=1.05 CJE=3.934e-11 VJE=0.680693 MJE=0.379312
+TF=2.75919e-10 XTF=0.674951 VTF=54426.6 ITF=0.067962
+CJC=2.40198e-11 VJC=0.4 MJC=0.462796 XCJC=1
+FC=0.570446 CJS=0 VJS=0.75 MJS=0.5
+TR=1e-07 PTF=0 KF=0 AF=1
.ENDL 2N2907A

.LIB BPW34
.subckt BPW34 Opt_In+ Opt_In- Cath Ano
+params: SENS=100 resp=50e-5 lens=1
G001 2 Ano Opt_In+ Opt_In- {SENS*resp*lens}
D1 Ano 2 F301
Rs 2 Cath 6.5
.model F301 D(IS=3.5e-11 N=1.01 IKF=6e-5 Cjo=73.01p M=0.452 Vj=0.304 BV=200)
.ends
.ENDL BPW34

.LIB LS_L296
.MODEL LS_L296_max_T D
+ IS=15.578E-24
+ N=1.6879
+ RS=8.9062
+ EG=2.6500
+ XTI=3
+ CJO=1.0000E-12

.MODEL LS_L296_typ_T D
+ IS=191.46E-24
+ N=1.6112
+ RS=3.9559
+ EG=2.4500
+ XTI=3
+ CJO=1.0000E-12

.MODEL LS_L296_min_T D
+ IS=6.8935E-21
+ N=1.6235
+ RS=.74794
+ EG=2.3100
+ XTI=3
+ CJO=1.0000E-12
.ENDL LS_L296

Makefile

SRC = circuit.sp library.sp

all: output.txt
	less output.txt

sim output.txt: $(SRC)
	ngspice <circuit.sp >temp.txt
	mv temp.txt output.txt

clean:
	-rm -f temp.txt output.txt

TODO

! Get rid of LT1932
~ Print interesting measurements