I'd like to make a low power one shot circuit, I'm planning to use a monost able oscillator to get my one shot functionality, but I was wondering what NPN transistor specs do I need to look for in order to get the lowest power circuit out of this? The circuit I'm building is below
link:
thanks!
oscillator to get my one shot functionality, but I was wondering what NPN transistor specs do I need to look for in order to get the lowest power circuit out of this? The circuit I'm building is below
High beta at low current. BCX70K maybe. Make sure you don't zener the e-b junctions.
Maybe you can use the UniShot circuit. It's like a 1-transistor monostable, sort of. You can build long strings of them. Fun.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
ostable oscillator to get my one shot functionality, but I was wondering wh at NPN transistor specs do I need to look for in order to get the lowest po wer circuit out of this? The circuit I'm building is below
e, sort
thank you sir,
so on my circuit, looks like my only current flow will be through R3, which if I pull it up to 3.3V and use a 10k gives me about 330uA going through i t, where do I start to push my limits here, if I have a 100k I end up at 33 uA, is this pushing it... I'm just wondering how to evaluate this... 10k is probally fine for what I'm doing but I'm just curious about how low I coul d bring my current... does the high beta take care of this?
Is the UniShot non-retriggable?
monostable oscillator to get my one shot functionality, but I was wondering what NPN transistor specs do I need to look for in order to get the lowest power circuit out of this? The circuit I'm building is below
[snip]sort
[snip]I pull it up to 3.3V and use a 10k gives me about 330uA going through it, where do I start to push my limits here, if I have a 100k I end up at 33uA, is this pushing it... I'm just wondering how to evaluate this... 10k is probally fine for what I'm doing but I'm just curious about how low I could bring my current... does the high beta take care of this?
Fun??? Oooops....
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| James E.Thompson | mens |
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I love to cook with wine. Sometimes I even put it in the food.
The above link has been re-posted, with a fix for the glitch... easy for those of us who actually understand transistors >:-} ...Jim Thompson
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stable oscillator to get my one shot functionality, but I was wondering wha t NPN transistor specs do I need to look for in order to get the lowest pow er circuit out of this? The circuit I'm building is below
Years ago (July 2008), we had a discussion here on making a low power oscil lator -"micro power square wave oscillator". The base-emitter capacitance o f the transistor involved turned out to be the feature that determined the current drawn at any sensible frequency, and the palm went to wide-band tra nsistors with Ft's of 5GHZ and higher.
I think I posted an LTSpice circuit using a pair of BFR92 transistors to cr eate a 100kHz oscillator. Jeorg went one better with BFP620's (which are mo re expensive and even more prone to oscillate, but faster). You need a "bas e-stopper" - something of the order of 33R in series with the base connecti on - to stop this kind of part from oscillating at few GHz, and you need to remember that base-emitter break-down voltage is only 2V in this kind of t ransistor.
-- Bill Sloman, Sydney
monostable oscillator to get my one shot functionality, but I was wondering what NPN transistor specs do I need to look for in order to get the lowest power circuit out of this? The circuit I'm building is below
sort
I pull it up to 3.3V and use a 10k gives me about 330uA going through it, where do I start to push my limits here, if I have a 100k I end up at 33uA, is this pushing it... I'm just wondering how to evaluate this... 10k is probally fine for what I'm doing but I'm just curious about how low I could bring my current... does the high beta take care of this?
It's not "Larkin's" uni-shot. It was widely used in model airplane r/c transmitters before ICs replaced it. And sure, you can make it not work if you really want to, and that's your skill set.
Hmmm, still is used, apparently
-- 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
And, after you tire of the BS, here's a toplevel of a model airplane R/C controller I did 12 years ago...
After all this time I can display all the guts if anyone is interested.
(It's configurable, AM or FM, the whole sheebang... receiver, double superhet, demod and decode, all on one chip.) ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Real R/C, LM1871 encoder, transmitter...
and LM1872 decoder...
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| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
monostable oscillator to get my one shot functionality, but I was wondering what NPN transistor specs do I need to look for in order to get the lowest power circuit out of this? The circuit I'm building is below
sort
if I pull it up to 3.3V and use a 10k gives me about 330uA going through it, where do I start to push my limits here, if I have a 100k I end up at 33uA, is this pushing it... I'm just wondering how to evaluate this... 10k is probally fine for what I'm doing but I'm just curious about how low I could bring my current... does the high beta take care of this?
Perhaps, with your "skill set", you'll provide us with component values that make it work? ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
nostable oscillator to get my one shot functionality, but I was wondering w hat NPN transistor specs do I need to look for in order to get the lowest p ower circuit out of this? The circuit I'm building is below
illator -"micro power square wave oscillator". The base-emitter capacitance of the transistor involved turned out to be the feature that determined th e current drawn at any sensible frequency, and the palm went to wide-band t ransistors with Ft's of 5GHZ and higher.
create a 100kHz oscillator. Jeorg went one better with BFP620's (which are more expensive and even more prone to oscillate, but faster). You need a "b ase-stopper" - something of the order of 33R in series with the base connec tion - to stop this kind of part from oscillating at few GHz, and you need to remember that base-emitter break-down voltage is only 2V in this kind of transistor.
thank you sir, I'll look into these
Those without "limited skill set" are invited to muse over WHY the base resistors I added get rid of the glitch sensitivity. ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
It forms a low pass filter with the base capacitance
Another way to fix it is to increase the collector resistors a bit. if the transistors aren't saturating you've got a high pass filter with unconstrained gain if they are you have sub-unity AC gain, and thus should be safe.
I had to reduce the collector resistors in LTSpice else I didn't get the glitches you were seeing
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Nope. It has to do with the base input characteristics.
Are you suggesting suicide bias? But you idea _will_ work, IF you pad the emitter with a resistor and then use a divider to set the bias rather than a single resistor... then you basically have a class-A stage.
Compare my wave-shapes, before and after the adding of the base series resistors. You'll note an important change.
Force a small timestep. ...Jim Thompson
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| James E.Thompson | mens |
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I love to cook with wine. Sometimes I even put it in the food.
Oooops! Left out the value. I ran it with TStepMax = 10ns ...Jim Thompson
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| James E.Thompson | mens |
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I love to cook with wine. Sometimes I even put it in the food.
I'm not familiar with that term ( googling "bipolar suicide bias" was no help :^) )
I'm seeing a failure mode where the voltage source beeing is pushing a pulse through tee B-C junctions of the transistors when it goes high, adding emitter resistors but leaving the base connected to the capacitor will likely make that glitch worse.
I'm seeing it run slightly faster. with increased input impedance of each stage the collector waveform output of the intermediate stages is squarer. that's about all.
10ns made no diference. neither did 1ns, except for increasing the run time. I dont see the glitches like in your PDF until I reduce the collector resistor to about 1KVersion 4 SHEET 1 940 680 WIRE 128 16 -32 16 WIRE 224 16 128 16 WIRE 320 16 224 16 WIRE 416 16 320 16 WIRE 512 16 416 16 WIRE 608 16 512 16 WIRE 704 16 608 16 WIRE 800 16 704 16 WIRE -32 32 -32 16 WIRE 128 32 128 16 WIRE 224 32 224 16 WIRE 320 32 320 16 WIRE 416 32 416 16 WIRE 512 32 512 16 WIRE 608 32 608 16 WIRE 704 32 704 16 WIRE 800 32 800 16 WIRE 48 128 16 128 WIRE 128 128 128 112 WIRE 128 128 112 128 WIRE 224 128 224 112 WIRE 240 128 224 128 WIRE 320 128 320 112 WIRE 320 128 304 128 WIRE 416 128 416 112 WIRE 432 128 416 128 WIRE 512 128 512 112 WIRE 512 128 496 128 WIRE 608 128 608 112 WIRE 624 128 608 128 WIRE 704 128 704 112 WIRE 704 128 688 128 WIRE 128 144 128 128 WIRE 320 144 320 128 WIRE 512 144 512 128 WIRE 704 144 704 128 WIRE 224 192 224 128 WIRE 224 192 208 192 WIRE 416 192 416 128 WIRE 416 192 400 192 WIRE 608 192 608 128 WIRE 608 192 592 192 WIRE 800 192 800 112 WIRE 800 192 784 192 WIRE 16 208 16 128 WIRE 128 240 128 224 WIRE 144 240 128 240 WIRE 320 240 320 224 WIRE 336 240 320 240 WIRE 512 240 512 224 WIRE 528 240 512 240 WIRE 704 240 704 224 WIRE 720 240 704 240 WIRE 224 288 208 288 WIRE 416 288 400 288 WIRE 608 288 592 288 WIRE 800 288 784 288 WIRE -32 304 -32 112 WIRE -16 304 -32 304 WIRE 16 304 16 288 WIRE 16 304 -16 304 WIRE 224 304 224 288 WIRE 224 304 16 304 WIRE 416 304 416 288 WIRE 416 304 224 304 WIRE 608 304 608 288 WIRE 608 304 416 304 WIRE 800 304 800 288 WIRE 800 304 608 304 WIRE -16 320 -16 304 FLAG 800 192 out FLAG -16 320 0 SYMBOL npn 144 192 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res 208 16 R0 WINDOW 0 41 29 Left 2 WINDOW 3 37 55 Left 2 SYMATTR InstName R1 SYMATTR Value {R_c} SYMBOL res 112 16 R0 WINDOW 3 35 76 Left 2 SYMATTR InstName R2 SYMATTR Value {R_b} SYMBOL cap 112 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 1n SYMBOL npn 336 192 R0 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL res 400 16 R0 WINDOW 0 41 29 Left 2 WINDOW 3 37 55 Left 2 SYMATTR InstName R3 SYMATTR Value {R_c} SYMBOL res 304 16 R0 SYMATTR InstName R4 SYMATTR Value {R_b} SYMBOL cap 304 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 1n SYMBOL npn 528 192 R0 SYMATTR InstName Q3 SYMATTR Value 2N3904 SYMBOL res 592 16 R0 WINDOW 0 41 29 Left 2 WINDOW 3 37 55 Left 2 SYMATTR InstName R5 SYMATTR Value {R_c} SYMBOL res 496 16 R0 SYMATTR InstName R6 SYMATTR Value {R_b} SYMBOL cap 496 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 1n SYMBOL npn 720 192 R0 SYMATTR InstName Q4 SYMATTR Value 2N3904 SYMBOL res 784 16 R0 WINDOW 0 41 29 Left 2 WINDOW 3 37 55 Left 2 SYMATTR InstName R7 SYMATTR Value {R_c} SYMBOL res 688 16 R0 SYMATTR InstName R8 SYMATTR Value {R_b} SYMBOL cap 688 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 1n SYMBOL voltage -32 16 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL voltage 16 192 R0 WINDOW 3 -10 135 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value PULSE(0 5 100u 100n 100n 600u 1 1) SYMBOL res 144 240 R180 WINDOW 0 -20 96 Left 2 WINDOW 3 -44 63 Left 2 SYMATTR InstName R9 SYMATTR Value {R_f} SYMBOL res 336 240 R180 WINDOW 0 -20 96 Left 2 WINDOW 3 -44 63 Left 2 SYMATTR InstName R10 SYMATTR Value {R_f} SYMBOL res 528 240 R180 WINDOW 0 -20 96 Left 2 WINDOW 3 -44 63 Left 2 SYMATTR InstName R11 SYMATTR Value {R_f} SYMBOL res 720 240 R180 WINDOW 0 -20 96 Left 2 WINDOW 3 -44 63 Left 2 SYMATTR InstName R12 SYMATTR Value {R_f} TEXT -34 -8 Left 2 !.tran 0 2m 0 10n TEXT 160 -16 Left 2 !.PARAM R_b=100k TEXT 336 -16 Left 2 !.PARAM R_c=1k TEXT 488 -16 Left 2 !.step PARAM R_f 0.00001 10000.00001 10000
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I suspect the difference is in the device models...
2N3904 Model in LTspice:.model 2N3904 NPN(IS=1E-14 VAF=100
.model Q2N3904 NPN(Is=6.734f Xti=3 Eg=1.11 Vaf=74.03
We're heading out to Wild Horse Pass Resort for Mother's Day Brunch,
16 of the family members (and member's to be... boy friends of granddaughters, and a fiance :-)So maybe it'll be a day or two, but I'll run several comparisons... run Beta curves for both transistors... note the GROSS IKF difference, the BR difference and the number of parameters LTspice assumes as default. Those differences have interesting effects on the Beta versus current... you will be surprised.
Then I'll import my .CIR file into LTspice. I would expect identical results for an identical setup (maybe :-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
[snip] [snip]
A quicky of the beta versus current at VCE=0.5V:
Everything is always perfection and light in LTspice (if you use the provided models)... be sure to use manufacturer-provided models to be safe. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
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