Diode-Bridge Voltage-Controlled Attenuator - simulation/decks/large_vc_2.cir

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John Lauer Saif Abdessayed's diode-bridge VCA: KiCad project, Gerbers, BOM, simulations, reports, and the earlier RC filter test 45f3ff6 11d ago

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* Diode-bridge voltage-controlled attenuator
* Actual ngspice model: ideal voltage buffer, high-gain control servo,
* onsemi-like 1N4148 and 2N3904 compact models, exact schematic passives.
.param VC=2
.param VINPP=12
.param FREQ=1k
VCC vcc 0 12
VEE vee 0 -12
VCTRL ctrl 0 {VC}
RCTRL ctrl ctrlf 10k
RCTRLPD ctrlf 0 1meg
CCTRL ctrlf 0 100n
VIN in 0 SIN(0 {VINPP/2} {FREQ}) AC 1
RIN in bufin 1k
RINPD bufin 0 1meg
E_BUF buf 0 bufin 0 1
RSER buf out 2.2k
RLOAD out 0 100k
CC1 out bra 220u ic=0
RCC1 bra bra_i 0.20
CC2 brb_i 0 220u ic=0
RCC2 brb brb_i 0.20
D1 brp bra_i D4148A
D2 brp brb D4148A
D3 bra_i brn D4148A
D4 brb brn D4148A
RFEED vcc brp 22k
BOP opout 0 V=max(-11,min(11,1e5*(V(ctrlf)-V(sense))))
RBASE opout base 4.7k
Q1 brn base sense Q2N3904
RE sense 0 8.06k
RLEAKP brp 0 100meg
RLEAKN brn 0 100meg
RLEAKA bra_i 0 100meg
RLEAKB brb 0 100meg
.model D4148A D(Is=4.352n Rs=0.6458 N=1.906 Cjo=7.048p M=0.5 Vj=0.869 Tt=3.48n Bv=100 Ibv=0.1u)
.model D4148B D(Is=4.439n Rs=0.6458 N=1.906 Cjo=7.048p M=0.5 Vj=0.869 Tt=3.48n Bv=100 Ibv=0.1u)
.model Q2N3904 NPN(Is=6.734f Xti=3 Eg=1.11 Vaf=74.03 Bf=416.4 Ne=1.259 Ise=6.734f Ikf=66.78m Xtb=1.5 Br=0.7371 Nc=2 Isc=0 Ikr=0 Rc=1 Cjc=3.638p Mjc=0.3085 Vjc=0.75 Fc=0.5 Cje=4.493p Mje=0.2593 Vje=0.75 Tr=239.5n Tf=301.2p Itf=0.4 Vtf=4 Xtf=2 Rb=10)

.tran 1u 30m 10m
.measure tran vout_pp PP v(out) from=20m to=30m
.measure tran vin_pp PP v(in) from=20m to=30m
.measure tran gain param='vout_pp/vin_pp'
.four 1k v(out)
.end