Electronics Workbench, Software

Discrete LM3909 LED Flasher: Circuit Variations

The basic discrete LM3909 LED Flasher circuit looks like this:

Discrete LM3909 - basic circuit
Discrete LM3909 – basic circuit

The LM3909 IC boosted a single 1.5 V cell enough to fire a red(-ish) LED, even with the cell well under 1 V. I want to blink a blue(-ish) LED from a pair of AA alkaline cells (with the right size & heft to serve as a base for the hairball circuitry), so the voltage ranges from just over 3 V down to maybe 1.5 V. Although the original circuit works, the LED pulse is long enough to put a reverse bias on the timing capacitor; a 470 µF electrolytic cap (positive terminal on the right at node P2-OUT) produces a pulse every few seconds.

A slightly tweaked version of the circuitry puts -400 mV across C1 (green trace) by the end of the pulse:

Discrete LM3909 - basic circuit - 3.0 V simulation
Discrete LM3909 – basic circuit – 3.0 V simulation

The App Note describes the negative feedback loop from the collector of “power transistor” Q3 through Q4 and Q1, closing through the Q2 current mirror. The base-emitter drops of Q4 and Q1 set the trip point where Q1 starts to conduct and the LED turns on.

Q3 is on when the LED is on, with C1 reverse-charging through R1 and the LED. The voltage at the top of R2 rises from the negative voltage at the start of the pulse, carrying the emitter of Q1 along with it. The LED pulse will end when the rising emitter voltage shuts off Q1 and, thus, the Q2 current mirror driving Q3. Because Q3 holds the bottom of R5 close to 0 V, the base of Q4 is at about half the supply voltage, so Q1 remains on until its emitter rises to about 2 forward drops (handwavingly ignoring the R6 + R7 voltage divider) below the supply.

If the LED pulse is longer than required to completely discharge C1, the poor cap gets reverse-biased and suffers indigestion. Aluminum electrolytics can withstand a little reverse bias, but it’s Bad Practice.

When Q3 and the LED are off, C1 forward-charges through (R4 + R5) + R2, with most of the initial voltage across R2, because C1 should start with a little more than 0 V across it. This holds the current mirror off until C1 charges enough to raise the base of Q4 about two forward drops above Q1’s emitter, shove current through Q4 and Q1, turn on the Q2 current mirror, Q3, and light the LED.

Around and around it goes!

The worst case for reverse charge happens at higher supply (a.k.a. battery) voltages and higher LED currents. Reducing the reverse charge time requires more forward drop through Q4 + Q1 to soak up the higher voltage and lower the trip voltage at Q1’s emitter, which suggests putting another forward-biased junction in series.

Putting a diode in Q1’s base lead doesn’t produce much improvement:

Discrete LM3909 - Q1 B diode - 3.0 V
Discrete LM3909 – Q1 B diode – 3.0 V

Perhaps because the 27 µA current at the trip point is so low the diode doesn’t actually have much forward drop; the simulation says 400 mV.

Putting the diode in the emitter runs the current mirror’s 5 mA through it:

Discrete LM3909 - Q1 E diode - 3.0 V
Discrete LM3909 – Q1 E diode – 3.0 V

The overall period remains about 2 s, but the LED pulse = reverse charge time drops by a factor of two and the cap voltage bottoms out at 0 V, so that’s good.

A Darlington transistor provides far more gain to compensate for the reduced base drive:

Discrete LM3909 - Darl Q1 - 3.0 V
Discrete LM3909 – Darl Q1 – 3.0 V

The LED pulse is slightly shorter and its current goes up a smidge, but the cap voltage remains above zero.

A line in the LM3909 App Note mentions that the Q2 current mirror amplifies Q1’s emitter current by a factor of three: “This current will be amplified by about 3 by Q2 and passed to the base of Q3”. An IC current mirror’s designer can scale its output by varying the collector area, but out here in the discrete world we must splice multiple transistors in parallel:

Discrete LM3909 - Darl Q1 3xQ2- 3.0 V
Discrete LM3909 – Darl Q1 3xQ2- 3.0 V

More base drive in Q3 doesn’t buy much, because it’s already pretty well saturated during the pulse, but the current goes up enough to push C1 slightly into reverse charge territory again. As far as I can tell, the factor-of-three gain was required to make up for the relatively poor performance of IC technology around 1970; things have definitely improved since then.

It’s worth mentioning that the actual circuitry (in particular, the LEDs!) will differ from the simulations, so the pretty plots are more along the lines of serving suggestions than actual predictions. Verily, a simulation can’t prove that a circuit will work, but can sometimes help show why it won’t.

All the LTSpice simulation files tucked into a GitHub Gist:

Version 4
SHEET 1 1816 760
WIRE 64 -16 0 -16
WIRE 112 -16 64 -16
WIRE 272 -16 112 -16
WIRE 544 -16 272 -16
WIRE 1024 -16 544 -16
WIRE 1200 -16 1024 -16
WIRE 112 0 112 -16
WIRE 272 0 272 -16
WIRE 1024 32 1024 -16
WIRE 1200 32 1200 -16
WIRE 0 48 0 -16
WIRE 544 48 544 -16
WIRE 944 80 864 80
WIRE 960 80 944 80
WIRE 1136 80 1104 80
WIRE 272 96 272 80
WIRE 400 96 272 96
WIRE 480 96 400 96
WIRE 400 112 400 96
WIRE 112 128 112 80
WIRE 272 128 272 96
WIRE 688 128 640 128
WIRE 800 128 752 128
WIRE 944 144 944 80
WIRE 1024 144 1024 128
WIRE 1024 144 944 144
WIRE 1104 144 1104 80
WIRE 1104 144 1024 144
WIRE 112 160 112 128
WIRE 864 192 864 176
WIRE 912 192 864 192
WIRE 0 208 0 128
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WIRE 640 208 640 128
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WIRE 400 224 400 208
WIRE 112 272 112 224
WIRE 128 272 112 272
WIRE 224 272 192 272
WIRE 272 272 272 208
WIRE 272 272 224 272
WIRE 912 272 912 192
WIRE 400 336 400 304
WIRE 544 336 544 144
WIRE 544 336 400 336
WIRE 112 368 112 272
WIRE 912 368 912 352
WIRE 912 368 112 368
WIRE 272 400 272 272
WIRE 112 416 112 368
WIRE 1200 448 1200 128
WIRE 1200 448 336 448
WIRE 112 464 112 416
WIRE 400 480 400 336
WIRE 0 496 0 288
WIRE 0 496 -32 496
WIRE -32 528 -32 496
WIRE 0 576 0 496
WIRE 64 576 0 576
WIRE 112 576 112 544
WIRE 112 576 64 576
WIRE 272 576 272 496
WIRE 272 576 112 576
WIRE 400 576 400 560
WIRE 400 576 272 576
FLAG -32 528 0
FLAG 112 128 P6-RLIM
FLAG 112 416 P18-RC
FLAG 224 272 P2-OUT
FLAG 64 -16 P5-V+
FLAG 64 576 P4-V-
SYMBOL res 96 -16 R0
SYMATTR InstName R1
SYMATTR Value 39
SYMBOL LED 96 160 R0
SYMATTR InstName D1
SYMATTR Value LXHL-BW02
SYMBOL res 96 448 R0
SYMATTR InstName R2
SYMATTR Value 9.1k
SYMBOL cap 192 256 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
WINDOW 40 52 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 1m
SYMATTR SpiceLine2 ic=0.5
SYMBOL res 256 112 R0
SYMATTR InstName R5
SYMATTR Value 390
SYMBOL res 256 -16 R0
SYMATTR InstName R4
SYMATTR Value 390
SYMBOL npn 336 400 M0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res 384 96 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL res 384 208 R0
SYMATTR InstName R7
SYMATTR Value 10k
SYMBOL res 384 464 R0
SYMATTR InstName R8
SYMATTR Value 20k
SYMBOL npn 480 48 R0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL npn 800 80 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL pnp 960 128 M180
SYMATTR InstName Q2a
SYMATTR Value 2N3906
SYMBOL voltage 0 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 116 Left 2
SYMATTR InstName V1
SYMATTR Value 1.5
SYMBOL res 896 256 R0
SYMATTR InstName R9
SYMATTR Value 100
SYMBOL pnp 1136 128 M180
SYMATTR InstName Q2b
SYMATTR Value 2N3906
SYMBOL res -16 32 R0
SYMATTR InstName PTC
SYMATTR Value 5
SYMBOL diode 688 144 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D2
SYMATTR Value 1N4148
TEXT -56 192 VRight 2 ;AA Alkaline
TEXT 512 528 Left 2 !.tran 30
TEXT 504 496 Left 2 ;Pins 3 and 7 = no connect
TEXT 760 488 Left 2 ;Sorted by Vd at If=20 mA \n \nPart # Mfg Is (A) N Iave (A) Vf@Iave (V) Vd@If (V)\nQTLP690C Fairchild 1.00E-22 1.500 0.16 1.90 1.82\nPT-121-B Luminous 4.35E-07 8.370 20.00 3.84 2.34\nLUW-W5AP OSRAM 6.57E-08 7.267 2.00 3.26 2.39\nLXHL-BW02 Lumileds 4.50E-20 2.600 0.40 2.95 2.75\nW5AP-LZMZ-5K Lumileds 3.50E-17 3.120 2.00 3.13 2.76\nLXK2-PW14 Lumileds 3.50E-17 3.120 1.60 3.11 2.76\nAOT-2015 AOT 5.96E-10 6.222 0.18 3.16 2.80\nNSSW008CT-P Nichia 2.30E-16 3.430 0.04 2.92 2.86\nNSSWS108T Nichia 1.13E-18 3.020 0.04 2.99 2.94\nNSPW500BS Nichia 2.70E-10 6.790 0.03 3.27 3.20\nNSCW100 Nichia 1.69E-08 9.626 0.03 3.60 3.50
TEXT 168 256 Left 4 ;+
TEXT 656 56 Left 2 ;3 V battery needs more VBE
view raw Discrete LM3909 - D2 Q1.asc hosted with ❤ by GitHub
Version 4
SHEET 1 1816 760
WIRE 64 -16 0 -16
WIRE 112 -16 64 -16
WIRE 272 -16 112 -16
WIRE 544 -16 272 -16
WIRE 1024 -16 544 -16
WIRE 1200 -16 1024 -16
WIRE 112 0 112 -16
WIRE 272 0 272 -16
WIRE 1024 32 1024 -16
WIRE 1200 32 1200 -16
WIRE 0 48 0 -16
WIRE 544 48 544 -16
WIRE 848 80 736 80
WIRE 944 80 848 80
WIRE 960 80 944 80
WIRE 1136 80 1104 80
WIRE 272 96 272 80
WIRE 400 96 272 96
WIRE 480 96 400 96
WIRE 400 112 400 96
WIRE 112 128 112 80
WIRE 272 128 272 96
WIRE 672 128 640 128
WIRE 848 144 848 80
WIRE 944 144 944 80
WIRE 1024 144 1024 128
WIRE 1024 144 944 144
WIRE 1104 144 1104 80
WIRE 1104 144 1024 144
WIRE 112 160 112 128
WIRE 736 192 736 176
WIRE 784 192 736 192
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WIRE 640 208 640 128
WIRE 640 208 400 208
WIRE 400 224 400 208
WIRE 912 240 848 240
WIRE 112 272 112 224
WIRE 128 272 112 272
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WIRE 272 272 272 208
WIRE 272 272 224 272
WIRE 912 272 912 240
WIRE 400 336 400 304
WIRE 544 336 544 144
WIRE 544 336 400 336
WIRE 112 368 112 272
WIRE 912 368 912 352
WIRE 912 368 112 368
WIRE 272 400 272 272
WIRE 112 416 112 368
WIRE 1200 448 1200 128
WIRE 1200 448 336 448
WIRE 112 464 112 416
WIRE 400 480 400 336
WIRE 0 496 0 288
WIRE 0 496 -32 496
WIRE -32 528 -32 496
WIRE 0 576 0 496
WIRE 64 576 0 576
WIRE 112 576 112 544
WIRE 112 576 64 576
WIRE 272 576 272 496
WIRE 272 576 112 576
WIRE 400 576 400 560
WIRE 400 576 272 576
FLAG -32 528 0
FLAG 112 128 P6-RLIM
FLAG 112 416 P18-RC
FLAG 224 272 P2-OUT
FLAG 64 -16 P5-V+
FLAG 64 576 P4-V-
SYMBOL res 96 -16 R0
SYMATTR InstName R1
SYMATTR Value 39
SYMBOL LED 96 160 R0
SYMATTR InstName D1
SYMATTR Value NSSW008CT-P1
SYMBOL res 96 448 R0
SYMATTR InstName R2
SYMATTR Value 9.1k
SYMBOL cap 192 256 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
WINDOW 40 52 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 470�
SYMATTR SpiceLine2 ic=0.5
SYMBOL res 256 112 R0
SYMATTR InstName R5
SYMATTR Value 390
SYMBOL res 256 -16 R0
SYMATTR InstName R4
SYMATTR Value 390
SYMBOL npn 336 400 M0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res 384 96 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL res 384 208 R0
SYMATTR InstName R7
SYMATTR Value 10k
SYMBOL res 384 464 R0
SYMATTR InstName R8
SYMATTR Value 20k
SYMBOL npn 480 48 R0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL npn 672 80 R0
SYMATTR InstName Q1a
SYMATTR Value 2N3904
SYMBOL pnp 960 128 M180
SYMATTR InstName Q2a
SYMATTR Value 2N3906
SYMBOL voltage 0 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 116 Left 2
SYMATTR InstName V1
SYMATTR Value 1.5
SYMBOL res 896 256 R0
SYMATTR InstName R9
SYMATTR Value 100
SYMBOL pnp 1136 128 M180
SYMATTR InstName Q2b
SYMATTR Value 2N3906
SYMBOL npn 784 144 R0
SYMATTR InstName Q1b
SYMATTR Value 2N3904
SYMBOL res -16 32 R0
SYMATTR InstName PTC
SYMATTR Value 5
TEXT -56 192 VRight 2 ;AA Alkaline
TEXT 512 528 Left 2 !.tran 30
TEXT 504 496 Left 2 ;Pins 3 and 7 = no connect
TEXT 760 488 Left 2 ;Sorted by Vd at If=20 mA \n \nPart # Mfg Is (A) N Iave (A) Vf@Iave (V) Vd@If (V)\nQTLP690C Fairchild 1.00E-22 1.500 0.16 1.90 1.82\nPT-121-B Luminous 4.35E-07 8.370 20.00 3.84 2.34\nLUW-W5AP OSRAM 6.57E-08 7.267 2.00 3.26 2.39\nLXHL-BW02 Lumileds 4.50E-20 2.600 0.40 2.95 2.75\nW5AP-LZMZ-5K Lumileds 3.50E-17 3.120 2.00 3.13 2.76\nLXK2-PW14 Lumileds 3.50E-17 3.120 1.60 3.11 2.76\nAOT-2015 AOT 5.96E-10 6.222 0.18 3.16 2.80\nNSSW008CT-P Nichia 2.30E-16 3.430 0.04 2.92 2.86\nNSSWS108T Nichia 1.13E-18 3.020 0.04 2.99 2.94\nNSPW500BS Nichia 2.70E-10 6.790 0.03 3.27 3.20\nNSCW100 Nichia 1.69E-08 9.626 0.03 3.60 3.50
TEXT 168 256 Left 4 ;+
TEXT 664 256 Left 2 ;Use MPSA14 Darlington
TEXT 656 56 Left 2 ;3 V battery needs more VBE
view raw Discrete LM3909 - Darl Q1 - 1X Q2 .asc hosted with ❤ by GitHub
Version 4
SHEET 1 1816 760
WIRE 64 -16 0 -16
WIRE 112 -16 64 -16
WIRE 272 -16 112 -16
WIRE 544 -16 272 -16
WIRE 1024 -16 544 -16
WIRE 1200 -16 1024 -16
WIRE 1360 -16 1200 -16
WIRE 1520 -16 1360 -16
WIRE 112 0 112 -16
WIRE 272 0 272 -16
WIRE 1024 32 1024 -16
WIRE 1200 32 1200 -16
WIRE 1360 32 1360 -16
WIRE 1520 32 1520 -16
WIRE 0 48 0 -16
WIRE 544 48 544 -16
WIRE 848 80 736 80
WIRE 944 80 848 80
WIRE 960 80 944 80
WIRE 1136 80 1104 80
WIRE 1296 80 1280 80
WIRE 1456 80 1440 80
WIRE 272 96 272 80
WIRE 400 96 272 96
WIRE 480 96 400 96
WIRE 400 112 400 96
WIRE 112 128 112 80
WIRE 272 128 272 96
WIRE 672 128 640 128
WIRE 848 144 848 80
WIRE 944 144 944 80
WIRE 1024 144 1024 128
WIRE 1024 144 944 144
WIRE 1104 144 1104 80
WIRE 1104 144 1024 144
WIRE 1280 144 1280 80
WIRE 1280 144 1104 144
WIRE 1440 144 1440 80
WIRE 1440 144 1280 144
WIRE 112 160 112 128
WIRE 736 192 736 176
WIRE 784 192 736 192
WIRE 1200 192 1200 128
WIRE 1360 192 1360 128
WIRE 1360 192 1200 192
WIRE 1520 192 1520 128
WIRE 1520 192 1360 192
WIRE 0 208 0 128
WIRE 400 208 400 192
WIRE 640 208 640 128
WIRE 640 208 400 208
WIRE 400 224 400 208
WIRE 912 240 848 240
WIRE 112 272 112 224
WIRE 128 272 112 272
WIRE 224 272 192 272
WIRE 272 272 272 208
WIRE 272 272 224 272
WIRE 912 272 912 240
WIRE 400 336 400 304
WIRE 544 336 544 144
WIRE 544 336 400 336
WIRE 112 368 112 272
WIRE 912 368 912 352
WIRE 912 368 112 368
WIRE 272 400 272 272
WIRE 112 416 112 368
WIRE 1200 448 1200 192
WIRE 1200 448 336 448
WIRE 112 464 112 416
WIRE 400 480 400 336
WIRE 0 496 0 288
WIRE 0 496 -32 496
WIRE -32 528 -32 496
WIRE 0 576 0 496
WIRE 64 576 0 576
WIRE 112 576 112 544
WIRE 112 576 64 576
WIRE 272 576 272 496
WIRE 272 576 112 576
WIRE 400 576 400 560
WIRE 400 576 272 576
FLAG -32 528 0
FLAG 112 128 P6-RLIM
FLAG 112 416 P18-RC
FLAG 224 272 P2-OUT
FLAG 64 -16 P5-V+
FLAG 64 576 P4-V-
SYMBOL res 96 -16 R0
SYMATTR InstName R1
SYMATTR Value 39
SYMBOL LED 96 160 R0
SYMATTR InstName D1
SYMATTR Value NSSW008CT-P1
SYMBOL res 96 448 R0
SYMATTR InstName R2
SYMATTR Value 9.1k
SYMBOL cap 192 256 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
WINDOW 40 52 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 470�
SYMATTR SpiceLine2 ic=0.5
SYMBOL res 256 112 R0
SYMATTR InstName R5
SYMATTR Value 390
SYMBOL res 256 -16 R0
SYMATTR InstName R4
SYMATTR Value 390
SYMBOL npn 336 400 M0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res 384 96 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL res 384 208 R0
SYMATTR InstName R7
SYMATTR Value 10k
SYMBOL res 384 464 R0
SYMATTR InstName R8
SYMATTR Value 20k
SYMBOL npn 480 48 R0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL npn 672 80 R0
SYMATTR InstName Q1a
SYMATTR Value 2N3904
SYMBOL pnp 960 128 M180
SYMATTR InstName Q2a
SYMATTR Value 2N3906
SYMBOL voltage 0 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 116 Left 2
SYMATTR InstName V1
SYMATTR Value 1.5
SYMBOL res 896 256 R0
SYMATTR InstName R9
SYMATTR Value 100
SYMBOL pnp 1136 128 M180
SYMATTR InstName Q2b
SYMATTR Value 2N3906
SYMBOL pnp 1296 128 M180
SYMATTR InstName Q2c
SYMATTR Value 2N3906
SYMBOL pnp 1456 128 M180
SYMATTR InstName Q2d
SYMATTR Value 2N3906
SYMBOL npn 784 144 R0
SYMATTR InstName Q1b
SYMATTR Value 2N3904
SYMBOL res -16 32 R0
SYMATTR InstName PTC
SYMATTR Value 5
TEXT -56 192 VRight 2 ;AA Alkaline
TEXT 512 528 Left 2 !.tran 15
TEXT 504 496 Left 2 ;Pins 3 and 7 = no connect
TEXT 760 488 Left 2 ;Sorted by Vd at If=20 mA \n \nPart # Mfg Is (A) N Iave (A) Vf@Iave (V) Vd@If (V)\nQTLP690C Fairchild 1.00E-22 1.500 0.16 1.90 1.82\nPT-121-B Luminous 4.35E-07 8.370 20.00 3.84 2.34\nLUW-W5AP OSRAM 6.57E-08 7.267 2.00 3.26 2.39\nLXHL-BW02 Lumileds 4.50E-20 2.600 0.40 2.95 2.75\nW5AP-LZMZ-5K Lumileds 3.50E-17 3.120 2.00 3.13 2.76\nLXK2-PW14 Lumileds 3.50E-17 3.120 1.60 3.11 2.76\nAOT-2015 AOT 5.96E-10 6.222 0.18 3.16 2.80\nNSSW008CT-P Nichia 2.30E-16 3.430 0.04 2.92 2.86\nNSSWS108T Nichia 1.13E-18 3.020 0.04 2.99 2.94\nNSPW500BS Nichia 2.70E-10 6.790 0.03 3.27 3.20\nNSCW100 Nichia 1.69E-08 9.626 0.03 3.60 3.50
TEXT 168 256 Left 4 ;+
TEXT 1224 224 Left 2 ;Current mirror with 3X current gain
TEXT 664 256 Left 2 ;Use MPSA14 Darlington
TEXT 656 56 Left 2 ;3 V battery needs more VBE
view raw Discrete LM3909 - Darl Q1 - 3X Q2 .asc hosted with ❤ by GitHub
Version 4
SHEET 1 1816 760
WIRE 64 -16 0 -16
WIRE 112 -16 64 -16
WIRE 272 -16 112 -16
WIRE 544 -16 272 -16
WIRE 1024 -16 544 -16
WIRE 1200 -16 1024 -16
WIRE 112 0 112 -16
WIRE 272 0 272 -16
WIRE 1024 32 1024 -16
WIRE 1200 32 1200 -16
WIRE 0 48 0 -16
WIRE 544 48 544 -16
WIRE 944 80 768 80
WIRE 960 80 944 80
WIRE 1136 80 1104 80
WIRE 272 96 272 80
WIRE 400 96 272 96
WIRE 480 96 400 96
WIRE 400 112 400 96
WIRE 112 128 112 80
WIRE 272 128 272 96
WIRE 704 128 640 128
WIRE 944 144 944 80
WIRE 1024 144 1024 128
WIRE 1024 144 944 144
WIRE 1104 144 1104 80
WIRE 1104 144 1024 144
WIRE 112 160 112 128
WIRE 768 192 768 176
WIRE 800 192 768 192
WIRE 912 192 864 192
WIRE 0 208 0 128
WIRE 400 208 400 192
WIRE 640 208 640 128
WIRE 640 208 400 208
WIRE 400 224 400 208
WIRE 112 272 112 224
WIRE 128 272 112 272
WIRE 224 272 192 272
WIRE 272 272 272 208
WIRE 272 272 224 272
WIRE 912 272 912 192
WIRE 400 336 400 304
WIRE 544 336 544 144
WIRE 544 336 400 336
WIRE 112 368 112 272
WIRE 912 368 912 352
WIRE 912 368 112 368
WIRE 272 400 272 272
WIRE 112 416 112 368
WIRE 1200 448 1200 128
WIRE 1200 448 336 448
WIRE 112 464 112 416
WIRE 400 480 400 336
WIRE 0 496 0 288
WIRE 0 496 -32 496
WIRE -32 528 -32 496
WIRE 0 576 0 496
WIRE 64 576 0 576
WIRE 112 576 112 544
WIRE 112 576 64 576
WIRE 272 576 272 496
WIRE 272 576 112 576
WIRE 400 576 400 560
WIRE 400 576 272 576
FLAG -32 528 0
FLAG 112 128 P6-RLIM
FLAG 112 416 P18-RC
FLAG 224 272 P2-OUT
FLAG 64 -16 P5-V+
FLAG 64 576 P4-V-
SYMBOL res 96 -16 R0
SYMATTR InstName R1
SYMATTR Value 39
SYMBOL LED 96 160 R0
SYMATTR InstName D1
SYMATTR Value LXHL-BW02
SYMBOL res 96 448 R0
SYMATTR InstName R2
SYMATTR Value 9.1k
SYMBOL cap 192 256 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
WINDOW 40 52 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 1m
SYMATTR SpiceLine2 ic=0.5
SYMBOL res 256 112 R0
SYMATTR InstName R5
SYMATTR Value 390
SYMBOL res 256 -16 R0
SYMATTR InstName R4
SYMATTR Value 390
SYMBOL npn 336 400 M0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res 384 96 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL res 384 208 R0
SYMATTR InstName R7
SYMATTR Value 10k
SYMBOL res 384 464 R0
SYMATTR InstName R8
SYMATTR Value 20k
SYMBOL npn 480 48 R0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL npn 704 80 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL pnp 960 128 M180
SYMATTR InstName Q2a
SYMATTR Value 2N3906
SYMBOL voltage 0 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 116 Left 2
SYMATTR InstName V1
SYMATTR Value 1.5
SYMBOL res 896 256 R0
SYMATTR InstName R9
SYMATTR Value 100
SYMBOL pnp 1136 128 M180
SYMATTR InstName Q2b
SYMATTR Value 2N3906
SYMBOL res -16 32 R0
SYMATTR InstName PTC
SYMATTR Value 5
SYMBOL diode 800 208 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D2
SYMATTR Value 1N4148
TEXT -56 192 VRight 2 ;AA Alkaline
TEXT 512 528 Left 2 !.tran 30
TEXT 504 496 Left 2 ;Pins 3 and 7 = no connect
TEXT 760 488 Left 2 ;Sorted by Vd at If=20 mA \n \nPart # Mfg Is (A) N Iave (A) Vf@Iave (V) Vd@If (V)\nQTLP690C Fairchild 1.00E-22 1.500 0.16 1.90 1.82\nPT-121-B Luminous 4.35E-07 8.370 20.00 3.84 2.34\nLUW-W5AP OSRAM 6.57E-08 7.267 2.00 3.26 2.39\nLXHL-BW02 Lumileds 4.50E-20 2.600 0.40 2.95 2.75\nW5AP-LZMZ-5K Lumileds 3.50E-17 3.120 2.00 3.13 2.76\nLXK2-PW14 Lumileds 3.50E-17 3.120 1.60 3.11 2.76\nAOT-2015 AOT 5.96E-10 6.222 0.18 3.16 2.80\nNSSW008CT-P Nichia 2.30E-16 3.430 0.04 2.92 2.86\nNSSWS108T Nichia 1.13E-18 3.020 0.04 2.99 2.94\nNSPW500BS Nichia 2.70E-10 6.790 0.03 3.27 3.20\nNSCW100 Nichia 1.69E-08 9.626 0.03 3.60 3.50
TEXT 168 256 Left 4 ;+
TEXT 656 56 Left 2 ;3 V battery needs more VBE
view raw Discrete LM3909 - Q1 D2.asc hosted with ❤ by GitHub
Version 4
SHEET 1 1812 680
WIRE 96 -16 32 -16
WIRE 144 -16 96 -16
WIRE 304 -16 144 -16
WIRE 544 -16 304 -16
WIRE 752 -16 544 -16
WIRE 144 0 144 -16
WIRE 304 0 304 -16
WIRE 752 0 752 -16
WIRE 928 0 752 0
WIRE 752 32 752 0
WIRE 928 32 928 0
WIRE 544 48 544 -16
WIRE 832 80 816 80
WIRE 864 80 832 80
WIRE 304 96 304 80
WIRE 400 96 304 96
WIRE 480 96 400 96
WIRE 400 112 400 96
WIRE 144 128 144 80
WIRE 304 128 304 96
WIRE 752 144 752 128
WIRE 752 144 704 144
WIRE 832 144 832 80
WIRE 832 144 752 144
WIRE 144 160 144 128
WIRE 704 160 704 144
WIRE 32 208 32 -16
WIRE 400 208 400 192
WIRE 640 208 400 208
WIRE 400 224 400 208
WIRE 704 272 704 256
WIRE 144 288 144 224
WIRE 160 288 144 288
WIRE 256 288 224 288
WIRE 304 288 304 208
WIRE 304 288 256 288
WIRE 400 320 400 304
WIRE 544 320 544 144
WIRE 544 320 400 320
WIRE 144 368 144 288
WIRE 704 368 704 352
WIRE 704 368 144 368
WIRE 304 400 304 288
WIRE 144 416 144 368
WIRE 928 448 928 128
WIRE 928 448 368 448
WIRE 144 464 144 416
WIRE 400 480 400 320
WIRE 32 496 32 288
WIRE 32 496 0 496
WIRE 0 528 0 496
WIRE 32 576 32 496
WIRE 96 576 32 576
WIRE 144 576 144 544
WIRE 144 576 96 576
WIRE 304 576 304 496
WIRE 304 576 144 576
WIRE 400 576 400 560
WIRE 400 576 304 576
FLAG 0 528 0
FLAG 144 128 P6-RLIM
FLAG 144 416 P18-RC
FLAG 256 288 P2-OUT
FLAG 96 -16 P5-V+
FLAG 96 576 P4-V-
SYMBOL res 128 -16 R0
SYMATTR InstName R1
SYMATTR Value 12
SYMBOL LED 128 160 R0
SYMATTR InstName D1
SYMATTR Value PT-121-B
SYMBOL res 128 448 R0
SYMATTR InstName R2
SYMATTR Value 9.1k
SYMBOL cap 224 272 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
WINDOW 40 52 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 470�
SYMATTR SpiceLine2 ic=0.5
SYMBOL res 288 112 R0
SYMATTR InstName R5
SYMATTR Value 390
SYMBOL res 288 -16 R0
SYMATTR InstName R4
SYMATTR Value 390
SYMBOL npn 368 400 M0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res 384 96 R0
SYMATTR InstName R6
SYMATTR Value 20k
SYMBOL res 384 208 R0
SYMATTR InstName R7
SYMATTR Value 10k
SYMBOL res 384 464 R0
SYMATTR InstName R8
SYMATTR Value 20k
SYMBOL npn 480 48 R0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL npn 640 160 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL pnp 816 128 R180
SYMATTR InstName Q2a
SYMATTR Value 2N3906
SYMBOL voltage 32 192 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 116 Left 2
SYMATTR InstName V1
SYMATTR Value 3
SYMBOL res 688 256 R0
SYMATTR InstName R9
SYMATTR Value 100
SYMBOL pnp 864 128 M180
SYMATTR InstName Q2b
SYMATTR Value 2N3906
TEXT -24 192 VRight 2 ;AA Alkaline
TEXT 512 528 Left 2 !.tran 10
TEXT 504 496 Left 2 ;Pins 3 and 7 = no connect
TEXT 1064 112 Left 2 ;Sorted by Vd at If=20 mA \n \nPart # Mfg Is (A) N Iave (A) Vf@Iave (V) Vd@If (V)\nQTLP690C Fairchild 1.00E-22 1.500 0.16 1.90 1.82\nPT-121-B Luminous 4.35E-07 8.370 20.00 3.84 2.34\nLUW-W5AP OSRAM 6.57E-08 7.267 2.00 3.26 2.39\nLXHL-BW02 Lumileds 4.50E-20 2.600 0.40 2.95 2.75\nW5AP-LZMZ-5K Lumileds 3.50E-17 3.120 2.00 3.13 2.76\nLXK2-PW14 Lumileds 3.50E-17 3.120 1.60 3.11 2.76\nAOT-2015 AOT 5.96E-10 6.222 0.18 3.16 2.80\nNSSW008CT-P Nichia 2.30E-16 3.430 0.04 2.92 2.86\nNSSWS108T Nichia 1.13E-18 3.020 0.04 2.99 2.94\nNSPW500BS Nichia 2.70E-10 6.790 0.03 3.27 3.20\nNSCW100 Nichia 1.69E-08 9.626 0.03 3.60 3.50
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