LTSpice: How do make a Schmitt oscillator run?

Started by Joerg in sci.electronics.design14 years ago 8 replies

Ok, simple circuit: Schmitt inverter, 10K resistor from output to input, 1000pF capacitor from input to ground. Vh set to about 20% of Vhigh....

Ok, simple circuit: Schmitt inverter, 10K resistor from output to input, 1000pF capacitor from input to ground. Vh set to about 20% of Vhigh. Should happily oscillate but I get the error message "Time step too small". Also there is a noted dip in voltage down to about 80%, something which should even be possible with a digital behavioral device. What gives? How can I fix that and make i...


How to select shunt capacitor for class E amplifier

Started by amal banerjee in sci.electronics.design3 years ago

Could some electronics guru please help ? I am trying to do some SPICE simulations for class E amplifiers. How is the shunt capacitor value...

Could some electronics guru please help ? I am trying to do some SPICE simulations for class E amplifiers. How is the shunt capacitor value calculated ? Any hints, suggestions would be helpful. Thanks in advance.


Breakdown voltage of PETG in Homemade Capacitor

Started by ngdbud in sci.electronics.design13 years ago 3 replies

I'm working on building a high voltage capacitor. I have heard that PET has a very high voltage breakdown. I came across an excellent source of...

I'm working on building a high voltage capacitor. I have heard that PET has a very high voltage breakdown. I came across an excellent source of PETG (Polyethylene Terphthalate Glycol). How much will this affect the puncture resistance? I did a bench test that went alright for being in open air. I'm confident it will handle the voltage I need, but I'd still like some solid numbers. Couldn't fi...


OT: Smartphone always charging destroyed battery?

Started by John Doe in sci.electronics.design3 years ago 54 replies

https://www.flickr.com/photos/27532210@N04/ Another Chinese battery bit the dust here. Noticed my smartphone was bulging, the screen was...

https://www.flickr.com/photos/27532210@N04/ Another Chinese battery bit the dust here. Noticed my smartphone was bulging, the screen was warping. The cause was obvious so, not having a torx t1 screwdriver, I ripped it apart. Tried using a capacitor in place of the stock battery but that didn't work. An 18650 works, but it's charged to 4.36 V. The smartphone is used for Wi-Fi security...


PSU capacitor choice

Started by Cursitor Doom in sci.electronics.design2 years ago 15 replies

Greetings, gentlemen, I'm attaching a scan of the rectifier board from an HP8547A network analyser. I'm just wondering how the designer(s)...

Greetings, gentlemen, I'm attaching a scan of the rectifier board from an HP8547A network analyser. I'm just wondering how the designer(s) arrived at the choice of value for the caps across the incoming supply from the mains transformer secondary windings (the caps immediately before the bridge rectifiers)? In case you can't make it out, the values are 0.047uF, 0.22uF, 0.47uF and 0.04...


Favourite parts with off-label uses?

Started by Anonymous in sci.electronics.design2 years ago 142 replies

Following up on blocher's sterling work,(*) Many of us use parts off-label, often very successfully. A few examples: SAV-551+ pHEMTs make...

Following up on blocher's sterling work,(*) Many of us use parts off-label, often very successfully. A few examples: SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable. 74HC4352s make good flying-capacitor diff amp front ends. TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but...


simple opamp amplifier circuit

Started by panfilero in sci.electronics.design10 years ago 23 replies

I'm simulating on LTSpice, a simple amplifier circuit with a 2.5V offset, but if I don't include a capacitor on my input my output hits the...

I'm simulating on LTSpice, a simple amplifier circuit with a 2.5V offset, but if I don't include a capacitor on my input my output hits the rails... why is this? The link shows what I'm doing in LTSpice thanks http://i555.photobucket.com/albums/jj477/panfilero/Capture-1.jpg


I think I now know what the SAC722 is and the function of the board.

Started by Jamie in sci.electronics.design10 years ago 1 reply

Earlier I asked if any one had some data on a Motorola part "SAC722" and I have not had any response to it, however, I think I now have it...

Earlier I asked if any one had some data on a Motorola part "SAC722" and I have not had any response to it, however, I think I now have it all under the hood. These units appear to be TRIACs, and there are two of them in series, maybe for redundancy? Any way, there is a REED contact envelope in there with a couple of turns on it that monitors an 1/2 HP AC capacitor start motor. ...


fast ramp follies

Started by John Larkin in sci.electronics.design5 years ago 139 replies

OK, I need to charge a capacitor with a stable constant current. The desired slope is about a volt per nanosecond. So I did...

OK, I need to charge a capacitor with a stable constant current. The desired slope is about a volt per nanosecond. So I did this: https://dl.dropbox.com/u/53724080/Circuits/Fast_Ramp.JPG Things like this tend to oscillate, so I used a fairly slow, high-beta transistor, BCX71K. The ferrite in the collector is supposed to isolate the ramp cap from the transistor capacitance and make ...


Tantalum capacitor ESR

Started by Cursitor Doom in sci.electronics.design3 years ago 29 replies

Gentlemen, I took a crazy risk and got some axial Kemet tantalums off Ebay (purportedly genuine). These are visually identical to the...

Gentlemen, I took a crazy risk and got some axial Kemet tantalums off Ebay (purportedly genuine). These are visually identical to the originals out of one of my HP boat anchors. And the ESR figures are better than the equivalent new aluminium (aloominum if you're in the US) electrolytics. But are these ESRs low enough to be the real thing? Here's an example of the values I'm seeing: 3.3...


Dots on inductors

Started by Raveninghorde in sci.electronics.design10 years ago 20 replies

I read many years ago (National app note from memory) that one should connect the inner layer of an inductor to the switch in a buck regulator...

I read many years ago (National app note from memory) that one should connect the inner layer of an inductor to the switch in a buck regulator and the outer layer to the capacitor as the outer layer will then act as a screen. I don't know if it makes a difference in practice but it's free. With many modern inductors it is impossible to see how they are wound so the only indication of "po...


I thought I was smart enough

Started by amdx in sci.electronics.design3 years ago 6 replies

I'm try to help the guy with the LDR triggering a 555. I'm slowly walking him through it and now just triggering it with a wire momentarily to...

I'm try to help the guy with the LDR triggering a 555. I'm slowly walking him through it and now just triggering it with a wire momentarily to grd, to pull Pin 2 low, through a capacitor. But it won't trigger. Here's the circuit, what is needed to make the circuit trigger properly. > https://www.dropbox.com/s/fwxu5vqazzqist4/one%20shot%20wire.jpg?dl=0 Ignore the LDR for now I realize


Purpose of precision high-current series regulator's resistors and capacitor?

Started by Don Kuenz in sci.electronics.design3 years ago 32 replies

This question was originally posted to piclist. The TL431 datasheet contains "Figure 29. Precision High-Current Series Regulator." What's the...

This question was originally posted to piclist. The TL431 datasheet contains "Figure 29. Precision High-Current Series Regulator." What's the purpose of the 30 ? resistor, the 4.7 k? resistor, and the 0.01 ?F capacitor? Thank you, -- Don Kuenz KB7RPU There was a young lady named Bright Whose speed was far faster than light; She set out one day In a relative way And returned on


Crapacitors

Started by Anonymous in sci.electronics.design9 years ago 75 replies

4.7uF 6.3V X5R dC = -70% @ 6VDC (!!) http://psearch.murata.com/capacitor/product/GRM188R60J475ME19%23.pdf James

4.7uF 6.3V X5R dC = -70% @ 6VDC (!!) http://psearch.murata.com/capacitor/product/GRM188R60J475ME19%23.pdf James


Sharing idea, eliminating IO leakage currents

Started by Klaus Kragelund in sci.electronics.design3 years ago 6 replies

Hi This may have been done before, but for me it was a solution to a week long problem with a circuit Say you have a voltage you need to...

Hi This may have been done before, but for me it was a solution to a week long problem with a circuit Say you have a voltage you need to measure with an ADC, let say 10V We need a voltage divider to bring it down to ADC range. That divider is normally of high resistance to not load the signal to much The problem is the leakage current of the ADC and the sample/hold capacitor of the ADC...


vehicle battery supercapacitor kit ideas

Started by Jamie M in sci.electronics.design3 years ago 15 replies

Hi, I have installed and tested a supercap on a V8 engine as an experiment to avoid buying a new lead acid battery: Here is the supercap I...

Hi, I have installed and tested a supercap on a V8 engine as an experiment to avoid buying a new lead acid battery: Here is the supercap I used: https://www.ebay.com/itm/16V-83F-Farad-Capacitor-Super-Capacitor-2-7V-500F-With-Protection-Board -Module/223685920878 (16V-83F) I soldered ring terminals to it and bolted it directly to the 12V battery (in parallel with the battery). Be


Cap Multiplier, NOT a "gimmick"

Started by Jim Thompson in sci.electronics.design9 years ago 13 replies

Here's a way to do capacitor multiplication... limited only by OpAmp GBW product, and no resistive components until the OpAmps run out...

Here's a way to do capacitor multiplication... limited only by OpAmp GBW product, and no resistive components until the OpAmps run out of steam. Mathematically, this is the same way I did behavioral models for crummy capacitors such as X7R and Y5U, except I had ideal amplifiers, and equations and/or tables to des


X-capacitor failure modes?

Started by Joerg in sci.electronics.design9 years ago 49 replies

Folks, This afternoon I took the old HP-4191A apart. Yesterday in the middle of some measurements it went pop-pop-pop, loud, like...

Folks, This afternoon I took the old HP-4191A apart. Yesterday in the middle of some measurements it went pop-pop-pop, loud, like firecrackers. I ran over and turned it off, upon which the popping stopped. An immense amount of light-gray smoke wafted out and it had an odd stench to it. The stench lingered for hours. I can't find any source and upon powering it up the analyzer worked fin...


Motor starting switch

Started by Oppie in sci.electronics.design9 years ago 18 replies

pain in the tail, my FAIP H150 electric power washer died. The motor starting capacitor went (oozed out the side of plastic shell). Replaced it...

pain in the tail, my FAIP H150 electric power washer died. The motor starting capacitor went (oozed out the side of plastic shell). Replaced it with a similarly rated phenolic case starting cap but noticed it's getting very warm. More than likely the motor centrifugal switch is stuck closed. It is a TEFC motor so getting to the switch is a major pain. Not to mention that I don't see a re...


single transistor oscillator

Started by Vivek N in sci.electronics.design9 years ago 11 replies

I tried building a single transistor LED flasher like this...

I tried building a single transistor LED flasher like this : http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html I didn't have the recommended 2n2222 - I tried with a BC548, 2n2369 and 2n3055 - None of them work. I'm using a trimpot set to 2 kiloohms and a 470 microfarad capacitor. Instead of a 100 ohm resistor I put 3 superbright LEDs in series. I get 1.2 v...