Phil

On 08/14/2013 11:24 AM, John Larkin wrote:

Interesting idea, turning a bug into a feature like that--the JFET's C_GS becomes a coupling capacitor instead of a shunt. I'll have to try it out.

Here's one of the variations I've been playing with (this one doesn't have realistic parasitics, but putting those in makes a really ugly schematic).

Cheers

Phil Hobbs

Version 4 SHEET 1 880 680 WIRE -864 -912 -976 -912 WIRE -720 -912 -864 -912 WIRE -576 -912 -720 -912 WIRE -32 -912 -576 -912 WIRE -864 -880 -864 -912 WIRE -32 -864 -32 -912 WIRE -720 -832 -720 -912 WIRE -576 -816 -576 -912 WIRE -976 -784 -976 -848 WIRE -960 -784 -976 -784 WIRE -896 -784 -960 -784 WIRE -864 -784 -864 -800 WIRE -864 -784 -896 -784 WIRE -960 -752 -960 -784 WIRE -896 -752 -896 -784 WIRE -32 -752 -32 -784 WIRE -832 -704 -896 -704 WIRE -816 -704 -832 -704 WIRE -720 -704 -720 -752 WIRE -720 -704 -736 -704 WIRE -960 -640 -960 -656 WIRE -896 -640 -896 -656 WIRE -896 -640 -960 -640 WIRE -960 -624 -960 -640 WIRE -960 -432 -960 -544 WIRE -960 -432 -1072 -432 WIRE -896 -432 -960 -432 WIRE -576 -432 -576 -736 WIRE -576 -432 -896 -432 WIRE -1072 -400 -1072 -432 WIRE -800 -384 -832 -384 WIRE -672 -384 -720 -384 WIRE -896 -368 -896 -432 WIRE -672 -352 -672 -384 WIRE -624 -352 -672 -352 WIRE -480 -352 -544 -352 WIRE -1072 -320 -1072 -336 WIRE -1072 -320 -1152 -320 WIRE -832 -320 -832 -384 WIRE -800 -320 -832 -320 WIRE -672 -320 -672 -352 WIRE -672 -320 -720 -320 WIRE -1072 -304 -1072 -320 WIRE -1152 -288 -1152 -320 WIRE -672 -288 -672 -320 WIRE -896 -208 -896 -272 WIRE -400 -208 -896 -208 WIRE -352 -208 -400 -208 WIRE -1152 -192 -1152 -224 WIRE -1072 -192 -1072 -224 WIRE -1072 -192 -1152 -192 WIRE -896 -176 -896 -208 WIRE -400 -160 -400 -208 WIRE -352 -160 -352 -208 WIRE -1168 -96 -1280 -96 WIRE -1072 -96 -1072 -192 WIRE -1072 -96 -1088 -96 WIRE -1008 -96 -1072 -96 WIRE -944 -96 -1008 -96 WIRE -576 -96 -608 -96 WIRE -448 -96 -496 -96 WIRE -400 -96 -448 -96 WIRE -304 -96 -400 -96 WIRE -1280 -80 -1280 -96 WIRE -1008 -48 -1008 -96 WIRE -816 -48 -1008 -48 WIRE -784 -48 -784 -96 WIRE -784 -48 -816 -48 WIRE -768 -48 -784 -48 WIRE -608 -48 -608 -96 WIRE -608 -48 -688 -48 WIRE -1008 -32 -1008 -48 WIRE -816 0 -816 -48 WIRE -768 0 -816 0 WIRE -608 0 -608 -48 WIRE -608 0 -688 0 WIRE -400 16 -400 -64 WIRE -352 16 -352 -64 WIRE -352 16 -400 16 WIRE -256 16 -352 16 WIRE -1280 32 -1280 0 WIRE -896 32 -896 -80 WIRE -736 32 -896 32 WIRE -672 32 -672 -224 WIRE -672 32 -736 32 WIRE -1008 64 -1008 32 WIRE -896 96 -896 32 WIRE -400 112 -400 16 WIRE -256 128 -256 96 WIRE -736 160 -736 32 WIRE -896 224 -896 176 WIRE -400 224 -400 192 WIRE -736 272 -736 224 WIRE -560 272 -736 272 WIRE -256 272 -256 208 WIRE -256 272 -480 272 WIRE -224 272 -256 272 WIRE -176 272 -192 272 WIRE -176 336 -176 272 FLAG -32 -752 0 FLAG -1280 32 0 FLAG -896 224 0 FLAG -400 224 0 FLAG -1008 64 0 FLAG -176 336 0 FLAG -480 -272 0 SYMBOL mesfet -944 -176 R0 SYMATTR InstName Q1 SYMATTR Value ATF38143_chip SYMBOL njf -448 -160 R0 SYMATTR InstName J1 SYMATTR Value BF862J SYMBOL voltage -32 -880 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V7 SYMATTR Value 10 SYMBOL voltage -1280 -96 R0 WINDOW 123 24 44 Left 2 WINDOW 39 0 0 Left 2 WINDOW 3 -59 194 Left 2 SYMATTR Value2 AC 1 0 SYMATTR Value PULSE(0 -10m 2n 10p 10p 100n 250n) SYMATTR InstName V8 SYMBOL current -896 96 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName I2 SYMATTR Value 45m SYMBOL cap -720 160 M0 SYMATTR InstName C1 SYMATTR Value 680p SYMBOL res -272 112 R0 SYMATTR InstName R3 SYMATTR Value 2 SYMBOL ind -272 0 R0 SYMATTR InstName L1 SYMATTR Value 150n SYMBOL njf -400 -160 R0 SYMATTR InstName J2 SYMATTR Value BF862J SYMBOL current -400 112 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName I1 SYMATTR Value 20m SYMBOL res -1184 -80 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R4 SYMATTR Value 9.5k SYMBOL npn -832 -368 M0 SYMATTR InstName Q7 SYMATTR Value BFP640FESD SYMATTR Prefix XN SYMBOL cap -688 -288 R0 SYMATTR InstName C3 SYMATTR Value 1u SYMBOL res -816 -304 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R6 SYMATTR Value 30 SYMBOL cap -1024 -32 R0 SYMATTR InstName C5 SYMATTR Value 1p SYMBOL ind -816 -368 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L3 SYMATTR Value 100n SYMBOL res -1088 -320 R0 SYMATTR InstName R9 SYMATTR Value 1k SYMBOL res -464 256 R90 WINDOW 0 -52 66 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R10 SYMATTR Value 4.5 SYMBOL cap -192 256 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C7 SYMATTR Value 1 SYMBOL cap -1088 -400 R0 SYMATTR InstName C6 SYMATTR Value 1m SYMBOL res -880 -896 R0 SYMATTR InstName R12 SYMATTR Value 19 SYMBOL ind -784 -32 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L5 SYMATTR Value {Lc} SYMBOL res -672 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value {Rc} SYMBOL cap -1168 -288 R0 SYMATTR InstName C8 SYMATTR Value 20f SYMBOL voltage -480 -96 R90 WINDOW 0 -32 56 VBottom 2 WINDOW 3 32 56 VTop 2 WINDOW 123 -4 56 VBottom 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 0 SYMATTR Value2 AC 0 SYMBOL cap -992 -912 R0 SYMATTR InstName C10 SYMATTR Value .02p SYMBOL voltage -480 -368 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 3.5 SYMBOL ind -640 -336 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L4 SYMATTR Value 1 SYMBOL pnp -832 -656 R180 SYMATTR InstName Q2 SYMATTR Value BFT93 SYMBOL voltage -720 -848 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value 2 SYMBOL res -592 -832 R0 SYMATTR InstName R1 SYMATTR Value 1k SYMBOL pnp -896 -656 R180 SYMATTR InstName Q3 SYMATTR Value BFT93 SYMBOL ind -944 -528 R180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L6 SYMATTR Value 1 SYMBOL ind -832 -688 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L7 SYMATTR Value 10 SYMATTR SpiceLine Rpar=60 TEXT -952 296 Left 2 !.tran 50n TEXT -1216 144 Left 2 ;Source current TEXT -1224 296 Left 2 ;Simulation command: TEXT -736 312 Left 2 !.lib c:\\electronics\\SpiceModels\\PHparts.lib TEXT -1224 224 Left 2 !.param Rs=3\n;.step dec param Rs 1 100 3 TEXT -1216 336 Left 2 !.options plotwinsize=0 TEXT -368 -392 Left 2 !.param Rc=85\n;.step param Rc 70 80 5\n.param Lc=300n\n;.step param Lc 180n 300n 40n

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

On 08/14/2013 12:56 PM, Phil Hobbs wrote:

Whoops, that one references a library. Here's a version with an output stage and all the parts included in the .asc file. Hopefully it survives line wrapping--it's also available at

Cheers

Phil Hobbs

Version 4 SHEET 1 4616 3540 WIRE -976 -912 -1056 -912 WIRE -864 -912 -976 -912 WIRE -720 -912 -864 -912 WIRE -256 -912 -720 -912 WIRE -32 -912 -256 -912 WIRE -864 -880 -864 -912 WIRE -32 -864 -32 -912 WIRE -720 -832 -720 -912 WIRE -1056 -816 -1056 -912 WIRE -976 -784 -976 -848 WIRE -960 -784 -976 -784 WIRE -864 -784 -864 -800 WIRE -864 -784 -960 -784 WIRE -960 -752 -960 -784 WIRE -32 -752 -32 -784 WIRE -720 -704 -720 -752 WIRE -720 -704 -896 -704 WIRE -1056 -640 -1056 -736 WIRE -960 -640 -960 -656 WIRE -960 -640 -1056 -640 WIRE -960 -624 -960 -640 WIRE -256 -560 -256 -912 WIRE -960 -512 -960 -544 WIRE -528 -512 -960 -512 WIRE -320 -512 -448 -512 WIRE -256 -448 -256 -464 WIRE -112 -448 -256 -448 WIRE -960 -432 -960 -512 WIRE -960 -432 -1072 -432 WIRE -896 -432 -960 -432 WIRE -1072 -400 -1072 -432 WIRE -256 -400 -256 -448 WIRE -800 -384 -832 -384 WIRE -672 -384 -720 -384 WIRE -896 -368 -896 -432 WIRE -672 -352 -672 -384 WIRE -624 -352 -672 -352 WIRE -480 -352 -544 -352 WIRE -1072 -320 -1072 -336 WIRE -1072 -320 -1152 -320 WIRE -832 -320 -832 -384 WIRE -800 -320 -832 -320 WIRE -672 -320 -672 -352 WIRE -672 -320 -720 -320 WIRE -1072 -304 -1072 -320 WIRE -1152 -288 -1152 -320 WIRE -672 -288 -672 -320 WIRE -256 -272 -256 -320 WIRE -896 -208 -896 -272 WIRE -400 -208 -896 -208 WIRE -352 -208 -400 -208 WIRE -1152 -192 -1152 -224 WIRE -1072 -192 -1072 -224 WIRE -1072 -192 -1152 -192 WIRE -896 -176 -896 -208 WIRE -400 -160 -400 -208 WIRE -352 -160 -352 -208 WIRE -1168 -96 -1280 -96 WIRE -1072 -96 -1072 -192 WIRE -1072 -96 -1088 -96 WIRE -1008 -96 -1072 -96 WIRE -944 -96 -1008 -96 WIRE -576 -96 -608 -96 WIRE -448 -96 -496 -96 WIRE -400 -96 -448 -96 WIRE -304 -96 -400 -96 WIRE -1280 -80 -1280 -96 WIRE -1008 -48 -1008 -96 WIRE -816 -48 -1008 -48 WIRE -784 -48 -784 -96 WIRE -784 -48 -816 -48 WIRE -768 -48 -784 -48 WIRE -608 -48 -608 -96 WIRE -608 -48 -688 -48 WIRE -1008 -32 -1008 -48 WIRE -816 0 -816 -48 WIRE -768 0 -816 0 WIRE -608 0 -608 -48 WIRE -608 0 -688 0 WIRE -400 16 -400 -64 WIRE -352 16 -352 -64 WIRE -352 16 -400 16 WIRE -256 16 -352 16 WIRE -1280 32 -1280 0 WIRE -896 32 -896 -80 WIRE -736 32 -896 32 WIRE -672 32 -672 -224 WIRE -672 32 -736 32 WIRE -1008 64 -1008 32 WIRE -896 96 -896 32 WIRE -400 112 -400 16 WIRE -256 128 -256 96 WIRE -736 160 -736 32 WIRE -896 224 -896 176 WIRE -400 224 -400 192 WIRE -736 272 -736 224 WIRE -560 272 -736 272 WIRE -256 272 -256 208 WIRE -256 272 -480 272 WIRE -224 272 -256 272 WIRE -176 272 -192 272 WIRE -176 336 -176 272 FLAG -32 -752 0 FLAG -1280 32 0 FLAG -896 224 0 FLAG -400 224 0 FLAG -1008 64 0 FLAG -176 336 0 FLAG -480 -272 0 FLAG -256 -272 0 FLAG -112 -448 out SYMBOL mesfet -944 -176 R0 SYMATTR InstName Q1 SYMATTR Value ATF38143_chip SYMBOL njf -448 -160 R0 SYMATTR InstName J1 SYMATTR Value BF862J SYMBOL voltage -32 -880 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V7 SYMATTR Value 10 SYMBOL voltage -1280 -96 R0 WINDOW 123 24 44 Left 2 WINDOW 39 0 0 Left 2 WINDOW 3 -59 194 Left 2 SYMATTR Value2 AC 1 0 SYMATTR Value PULSE(0 -10m 2n 10p 10p 100n 250n) SYMATTR InstName V8 SYMBOL current -896 96 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName I2 SYMATTR Value 45m SYMBOL cap -720 160 M0 SYMATTR InstName C1 SYMATTR Value 680p SYMBOL res -272 112 R0 SYMATTR InstName R3 SYMATTR Value 2 SYMBOL ind -272 0 R0 SYMATTR InstName L1 SYMATTR Value 150n SYMBOL njf -400 -160 R0 SYMATTR InstName J2 SYMATTR Value BF862J SYMBOL current -400 112 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName I1 SYMATTR Value 20m SYMBOL res -1184 -80 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R4 SYMATTR Value 9.5k SYMBOL npn -832 -368 M0 SYMATTR InstName Q7 SYMATTR Value BFP640FESD SYMATTR Prefix XN SYMBOL cap -688 -288 R0 SYMATTR InstName C3 SYMATTR Value 1u SYMBOL res -816 -304 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R6 SYMATTR Value 30 SYMBOL cap -1024 -32 R0 SYMATTR InstName C5 SYMATTR Value 1p SYMBOL ind -816 -368 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L3 SYMATTR Value 100n SYMBOL res -1088 -320 R0 SYMATTR InstName R9 SYMATTR Value 1k SYMBOL res -464 256 R90 WINDOW 0 -52 66 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R10 SYMATTR Value 4.5 SYMBOL cap -192 256 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C7 SYMATTR Value 1 SYMBOL cap -1088 -400 R0 SYMATTR InstName C6 SYMATTR Value 1m SYMBOL res -880 -896 R0 SYMATTR InstName R12 SYMATTR Value 19 SYMBOL ind -784 -32 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L5 SYMATTR Value {Lc} SYMBOL res -672 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value {Rc} SYMBOL cap -1168 -288 R0 SYMATTR InstName C8 SYMATTR Value 20f SYMBOL voltage -480 -96 R90 WINDOW 0 -32 56 VBottom 2 WINDOW 3 32 56 VTop 2 WINDOW 123 -4 56 VBottom 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 0 SYMATTR Value2 AC 0 SYMBOL cap -992 -912 R0 SYMATTR InstName C10 SYMATTR Value .02p SYMBOL voltage -480 -368 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 3.5 SYMBOL ind -640 -336 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L4 SYMATTR Value 1 SYMBOL voltage -720 -848 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value 2 SYMBOL res -1072 -832 R0 SYMATTR InstName R1 SYMATTR Value 1k SYMBOL pnp -896 -656 R180 SYMATTR InstName Q3 SYMATTR Value 2N4403 SYMBOL ind -944 -528 R180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L6 SYMATTR Value 1u SYMATTR SpiceLine Rpar=1k SYMBOL npn -320 -560 R0 SYMATTR InstName Q2 SYMATTR Value BFP640FESD SYMATTR Prefix XN SYMBOL res -272 -416 R0 SYMATTR InstName R2 SYMATTR Value 500 SYMBOL ind -544 -496 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L2 SYMATTR Value 100n SYMATTR SpiceLine Rpar=150 TEXT -952 296 Left 2 !.tran 5n TEXT -1216 144 Left 2 ;Source current TEXT -1224 296 Left 2 ;Simulation command: TEXT -1224 224 Left 2 !.param Rs=3\n;.step dec param Rs 1 100 3 TEXT -1216 336 Left 2 !.options plotwinsize=0 TEXT -232 -248 Left 2 !.param Rc=85\n;.step param Rc 70 80 5\n.param Lc=300n\n;.step param Lc 180n 300n 40n TEXT -1704 352 Invisible 2 !.MODEL ATF38143_chip NMF( vto=-0.75, Beta=0.3, Lambda=0.07, Alpha=4, B=0.8, Pb=0.7, Cgs=0.997E-12, Cgd=0.176E-12, Rd=0.084, Rs=0.054, Kf=1e6, Af=1) TEXT -1872 368 Invisible 2 !.model BF862J NJF(Beta=47.800E-3 Betatce=-.5 Rd=.8 Rs=7.5000 Lambda=37.300E-3 Vto=-.57093 Vtotc=-2.0000E-3 Is=424.60E-12 Isr=2.995p N=1 Nr=2 Xti=3 Alpha=-1.0000E-3 Vk=59.97 Cgd=7.4002E-12 M=.6015 Pb=.5 Fc=.5 Cgs=8.2890E-12 Kf=87.5E-18 Af=1); TEXT -2192 -1008 Invisible 2 !.model BFT93 PNP( IS = 8.3513E-016 BF = 48.565 NF = 1.00043 VAF = 19.012 IKF = .146824 ISE = 9.0946E-014 NE = 1.7493 BR = 12.183 NR = .99769 VAR = 3.3749 IKR = 6.7427E-003 ISC = 2.343E-014 NC = 1.4499 RB = 10 IRB = 1E-006 RBM = 10 RE = .2 RC =

3.8 EG = 1.11 XTI = 3 CJE = 1.57034E-012 VJE = .6 MJE = .3822 TF = 1.4853E-011 XTF = 2.2097 VTF = 2.9899 ITF = 1.4372E-002 CJC = 1.9953E-012 VJC = .5845 MJC = .28132 XCJC = .12 TR = 3E-009 VJS = .75 FC = .811678) TEXT -1800 472 Invisible 2 !.SUBCKT BFP640FESD 1 2 3\nCBEPAR 22 33 3.13946E-013\nCBCPAR 22 11 2.787E-014\nCCEPAR 11 33 3.39308E-015\nLB 22 20 5.04561E-010\nLE 33 30 9.88791E-011\nLC 11 10 5.104E-010\nCBEPCK 20 30 5.49758E-014\nCBCPCK 20 10 8.469E-015\nCCEPCK 10 30 1.00975E-014\nLBX 20 2 4.005E-011\nLEX 30 3 4.176E-011\nLCX 10 1 2.07E-011\n \n \nD1 33 25 M_D1\nD2 26 25 M_D2\nRBLfdb 22 25 3.2\nRPWf 33 26 7.64\nRPWe 33 16 11.27\nRSf 26 4 477\nRSe 16 4 350\nRCs 44 4 0.26\nRSUB 30 4 0.01\nD3 16 15 M_D3\nD4 23 33 M_D4\nD5 23 15 M_D5\nRLDNBL 15 11 14.8\n \n \nQ1 11 22 33 44 M_BFP640FESD\n \n \n.MODEL M_D1 D(\n+ IS=3.5E-015\n+ N=1.02\n+ RS=6.1\n+ CJO=2E-014)\n \n \n.MODEL M_D2 D(\n+ IS=3.5E-015\n+ N=1.02\n+ RS=0\n+ CJO=2.25E-014)\n \n \n.MODEL M_D3 D(\n+ IS=3.5E-015\n+ N=1.02\n+ RS=0\n+ CJO =9.57E-014)\n \n \n.MODEL M_D4 D(\n+ IS=3.5E-015\n+ N=1.02\n+ RS=0.2\n+ CJO =3E-014)\n \n.MODEL M_D5 D(\n+ IS=3.5E-015\n+ N=1.02\n+ RS=4.7\n+ CJO =3E-014)\n \n \n \n \n.MODEL M_BFP640FESD NPN(\n+ IS = 1.542E-015\n+ BF = 642.6\n+ NF = 1.014\n+ VAF = 355.5\n+ IKF = 0.1782\n+ ISE = 3.98E-015\n+ NE = 1.737\n+ BR = 49.18\n+ NR = 0.98\n+ VAR = 1.378\n+ IKR = 0.1924\n+ ISC = 3.85E-015\n+ NC = 1.5\n+ RB = 6.00965\n+ IRB = 9.099E-006\n+ RBM = 1.74736\n+ RE = 0.0142\n+ RC = 4.54\n+ XTB = -2.514\n+ EG = 1.11\n+ XTI = 0.808\n+ CJE = 1.676E-013\n+ VJE = 0.6804\n+ MJE = 0.2508\n+ TF = 1.836E-012\n+ XTF = 2.279\n+ VTF = 0.9972\n+ ITF = 0.6365\n+ PTF = 0.2896\n+ CJC = 8.39234E-014\n+ VJC = 0.5464\n+ MJC = 0.3098\n+ XCJC = 0.6466\n+ TR = 1.489E-007\n+ CJS = 2.15519E-013\n+ MJS = 0.2426\n+ VJS = 0.29\n+ FC = 0.8156\n+ KF = 123.5E-12\n+ AF = 1.89)

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Cool. Use an LED for V3!

The other thing I was thinking was to keep the gate current of the phemt out of the input node.

Do you have any data on gate current and gate current noise vs frequency for that phemt? The data sheets sure don't.

Hey, I just got handed the first build of a new laser driver. This one can put 300 amps into a 25 volt bar laser, close to 8 kilowatts. It has the analog-multiplier fet SOAR protection, the realtime simulation of fet junction temperature. There's a tiny Zetex nickel RTD under one of those heat sinks.

The Brat does beautiful layouts.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation

The gate current is a few hundred pA near I_DSS, iirc. The 1/f corner is about 10 MHz, and the gate current noise is small even in the 1/f region.

The bad news is that those Avago things have drain impedances of like

150 ohms or something horrible like that, so they absolutely have to be cascoded if you're going to use them as a voltage amp. Cascoding them with SiGe:C NPNs is a big win--the very low emitter impedance fixes the wet-spaghetti drain, and the huge VAF lets you run a large voltage gain in one stage.

The Skyworks SKY65050 pHEMTs that I have exhibit zero gate current at some slightly depleted bias like -100 mV, which is weird but potentially useful. They also have dramatically higher drain impedances. They're a little noisier everywhere, like 0.45 nV vs 0.35, but their major drawback is that their 1/f corner is around 60 MHz.

Very pretty!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Curious me. What is the pulse width, John? And, I assume it is sort of exponential.

Thanks. John S

This is intended to drive bar lasers from, say, 20 us to as much as a millisecond maybe. Like for pumping YAGs or something. Rise/fall times are in the 5 us range, pretty slow. At 300 amps, we'll be discharging the caps fast, not to mention toasting the fets.

The usual YAGs have a fluorescence lifetime of something like 250 us, so there's no advantage to pumping them for longer.

It's a constant-current driver, so the current pulses are very, very flat.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation

I don't think I have that file.

Wow! You ARE fast. No sooner did I post a request for the .lib and HERE it is!