hybridfree/eevblog-posts huggingface dataset:
LTC1799IS5 Freq Drift Over Temp - Page 1
Forum section: electronics / beginners

author: AlexRG
author_rank: Regular Contributor
timestamp: May 03, 2025, 12:27:38 pm
content: Hello everyone. On the LTC1799IS5 chip, I decided to assemble a smooth range generator for the AM and SSB receiver. I connected the microcircuit according to the scheme.(the PCB is from another project, it just fits the placement of the chip)The supply voltage is very stable and does not affect the operation of the microcircuit. However, the temperature instability is very high 1.827.4MHz - 1.828.6MHz. Watch the video.For 1 minute, about 1.2-1.4kHz. This is still normal for AM, although not very good. But it definitely won't work for SSB.Question. Please look at the description of the microcircuithttps://www.lcsc.com/datasheet/lcsc_datasheet_2410121747_Analog-Devices-LTC1799IS5-TRMPBF_C89118.pdf, is this temperature instability normal for this LTC1799IS5? Or did I do something wrong?

author: Andree Henkel
author_rank: Regular Contributor
timestamp: May 05, 2025, 03:55:58 pm
content: (1.828.6MHz / 1.827.4MHz) - 1 gives (in %): 0,066% or 660ppmin datasheet temperature dependance of frequency of the LTC1799 is given by 40ppm/°Cso 660ppm would result from 660/40 = 16,5°C Temperature change.However this misses the influence of the temperature dependence of your resistor R2 and Trimmer R1, they are likely larger source of temperature drift than LTC1799 itselv.Standard resistors (R2) have typically 100ppm, cermet trimmers have 100ppm, carbon potentiometers have lot larger temperature coefficient.So likely most of your temperature variation in frequency is from the two resistors
LTC2422 and external clock - Page 1
Forum section: electronics / beginners

author: ggchab
author_rank: Frequent Contributor
timestamp: April 09, 2017, 11:18:54 am
content: Hello, I am using an LTC2422 to read the output voltage and current of a power supply (based on Gerry Sweeney's design). To make some experiments, I connected the Fo pin of the ADC to a PWM output pin of the Microchip PIC I am using to control the power supply (18F25K22). When Fo is low or high, no problem, the ADC is working correctly.To try to maximize the number of conversions per second, I configured the PWM module to produce a 302KHz signal that follows the datasheet specifications (less then 307.2 KHz, high and low periods greater then 0.5µs - verified with an oscilloscope). In that case, the ADC is no longer converting correctly: the EXR bit is almost always set to 1. Even if I decrease the frequency, this is still terrible. What am I doing wrong ? Thank you

author: ggchab
author_rank: Frequent Contributor
timestamp: April 13, 2017, 08:13:42 am
content: It looks as if a constant is subtracted from the converted value when the Fo pin of the LTC2422 is connected to an external clock. Therefore, when Vin is closed to zero, the converted value is negative. The value increases linearly with the increase of Vin and eventually becomes positive (around Vin = O.025V in my case). When the value is negative, the EXR bit is set to 1 even if Vin > 0.I don't understand why but, at least, I can use the converted values by simply adding a constant.

author: sanwal209
author_rank: Regular Contributor
timestamp: April 14, 2017, 07:32:31 pm
content: EXR bit=1 represents that your Vin is out of range. Check your vref voltage and vin voltage level.Also read the Frequency Rejection Selection (FO Pin Connection) section in datasheet.
LTC3454 PWM - Page 1
Forum section: electronics / beginners

author: ripper121
author_rank: Contributor
timestamp: November 23, 2016, 09:42:08 am
content: Hello,i want to use the LTC3454 for my Flashlight as a 1A Led Driver.For this i want to controle the LTC3454 via a PWM signal from a attiny85http://cds.linear.com/docs/en/datasheet/3454fa.pdfPage 11 shows how to connect this PWM signal. But i dont know which Resistor and Which Capacitor Values i should use for this.Also there are 2 ISET's. Is the first for the 0-500mA range and the second for the 500-1000mA?If yes, is the PWM signal for 500mA ISET1 PWMsignal 0-100% and for 1000mA ISET1 PWMsignal 100% + ISET2 PWMsignal 0-100%?

author: NottheDan
author_rank: Frequent Contributor
timestamp: November 23, 2016, 10:38:59 am
content: Quote from: ripper121 on November 23, 2016, 09:42:08 amErr, no. Look at page 8 on the data sheet the table at the bottom right.EN1EN2ILOAD (A)GNDGND0 (SHUTDOWN)VINGND3850 • 0.8V/RISET1GNDVIN3850 • 0.8V/RISET1VINVIN3850 • (0.8V/RISET1 + 0.8V/RISET2)

author: ripper121
author_rank: Contributor
timestamp: November 23, 2016, 10:42:20 am
content: Yeah but this is no PWM controle!And i dont think i can put a PWM signal to EN1 and EN2, because then they hadn't wrote a extra info about PWM.

author: kxenos
author_rank: Frequent Contributor
timestamp: November 23, 2016, 11:07:34 am
content: The resistor which is shown as Riset/100 and the capacitor form a low pass filter that converts the PWM signal into an analog voltage. Say you have duty cycle 20% and a 5V PWM signal then you will have about 0.2*5=1V on average. For this to work ok the f-3dB of this filter has to be at least 2 orders of magnitude lower than the freq of the PWM signal. For PWM freq of 10kHz that would be 1/(2piRC)=100.

author: danadak
author_rank: Super Contributor
timestamp: November 23, 2016, 12:51:01 pm
content: PWM Filter design, attached.Regards, Dana.

author: ripper121
author_rank: Contributor
timestamp: November 23, 2016, 01:11:46 pm
content: So i found a tool to calc this RC Filter.http://sim.okawa-denshi.jp/en/PWMtool.php
LTC3780 alternative - Page 1
Forum section: electronics / beginners

author: npelov
author_rank: Frequent Contributor
timestamp: June 15, 2024, 10:41:31 am
content: Hi,I was looking for efficient buck-boost DC-DC converter. I initially bought LTC3780 with CC from ebay/ali, but it can't really handle high currents, the CC circuit drops voltage too early. Also it wasn't that efficient. Then I found plain implementation (no CC circuit) which worked fine. I was powering a NAS with two HDDs and they are able to spin up. The NAS, 1 wifi router, 1 switch and 1 raspberry pi barely hit 5A during HDD spin up. The non-CC one also got up to 95% (roughly calculated).I wanted to implement this converter in my UPS bit I saw LTC3780 is low or no stock everywhere. Is there an equivalent synchronous SMPS IC that's recommended for new designs. I will use JLCPCB.
LTC3780 board - replacing trimmers with pots - Page 1
Forum section: electronics / beginners

author: bogdan2014
author_rank: Regular Contributor
timestamp: April 08, 2019, 03:53:01 pm
content: I got a pair of these boards and I want to build two variable bench power supplies out of them. I would like to replace the two trimpots V-adjust and I-adjust with actual panel potentiometers. I was initially looking for 10 turn pots but at those values (500k and 200k) they're pretty rare and expensive.I don't like the idea of having two of them for coarse and fine adjustment either, so is there a way to lower the value of the pots while retaining the whole range of voltage and current?Sent from my Poco F1 using Tapatalk

author: TimNJ
author_rank: Super Contributor
timestamp: April 09, 2019, 05:34:38 pm
content: Do you have a schematic for this board? If not, my guess is that they are using the application circuit, or something very similar.You can re-scale the output voltage/current networks quite easily. However, this may require re-compensating the error amplifier (pin ITH).See attached images.

author: LateLesley
author_rank: Frequent Contributor
timestamp: April 09, 2019, 06:03:26 pm
content: It may be possible. I had a look at the LTC3780 datasheet, and the voltage adjust seems to be done with a voltage divider, so it may be easy to change the pot value by changing the fixed resistor in the divider.https://www.analog.com/media/en/technical-documentation/data-sheets/LTC3780.pdfIf you look at page 21 it gives the equation for working out the voltage divider for the circuit on page 26 (R1, R2). So if you find the resistor(s) connected to the voltage pot, you should be able to find out which ones to change. It is entirely possible that they just used the pot across the output, and the wiper to the chip, in which case you could just swap the pot for any value without the need to change anything else, but you do want as high a resistance as possible, as it would be across the supply.The current might be a little more problematic, as i'm not sure the mechanism it is using to control that. I suspect it may be a pot connected to the ITHand fed from a voltage reference somewhere, so you might need to trace out its circuit before you get suggestions to change it.
Buck converter breaking with load transients - Page 1
Forum section: electronics / beginners

author: sapien
author_rank: Contributor
timestamp: November 14, 2022, 07:36:39 pm
content: Hi all!My first post on the forumI'm designing an LTC3892 based buck converter which has to be able to supply 12 or 24V @300W (in dual phase mode). The selection of an output voltage is done by externally manipulating the Vout feedback circuit (external signal connected at 'PWM' labeled header P2). This is my first time building such a switching power supply.Initially it worked (after adding the input and output bulk capacitors). However, with 1 or more load transients the IC has 1 or both channels breaking.I tried increasing the low-pass filter effect on Vin of the IC, by increasing the value of both R12 and C19. This helped, but not tremendously.A slightly more successful change was cutting the grounding trace from C19 to C39, and regrounding C19 by adding a wire to a different grounding point (see 'toplayer-added wire' and 'toplayer picture-added wire'. Note that in the picture a solderbridge between C19 and C39 is visible, which can be ignored). This was done in an effort to isolate the ground path of C39, which supplies a high peak current when charging the FET gates, from the C19 ground path. The ground path of C19 has a much lower current flowing through it (I think), but also has to be less noisy, to supply Vin with low-noise power. This alteration however got me to a maximum lifespan of something like 20 transient load tests, after which it lay on the shelf for a week, after which 1 channel had stopped working.Any advice on what the problem(s) might be, or even on how to find/analyze the problem?First time I'm designing such a complicated project, so any general tips are also very welcome!
ltc4006 - dual pullup ? - Page 1
Forum section: electronics / beginners

author: gionag
author_rank: Newbie
timestamp: June 09, 2016, 03:20:56 pm
content: Hello folks, it's my first post here... and i was too shy to post that to other, more advanced "section".I am starting to design a battery-pack charger around the ltc4006 ic from linear...i was reading the datasheet of the ltc and i've found this section :QuoteHow does it works ? i don't understand how can i detect three state by using two pullups... can you explain me ? The topic interest me because i am planning to implement an mcu to monitor the process (in conjunction with a supervisor ic from ti).thanks a lot !Michele

author: newbrain
author_rank: Super Contributor
timestamp: June 09, 2016, 05:11:51 pm
content: Ciao Michele, and welcome!As you can see from the picture you attached, there are two pull-ups attached to the /CHG pin:The fixed one, 200kohmA second one, that can be driven by the micro output.Now, let's consider the situations described in the datasheet.To be of some use the OUT pin from the µP must be set either to High or to HiZ (e.g. by setting it as an input), using it as a push-pull output will not help.First case: the internal N-chan MOSFET in the ltc4006 is turned on, and able to sink more than 100µA.In this case, regardless of the status of the OUT pin the level at the IN pin will be 0 or close to 0:Worst case is when OUT is driven High: VIN = 3.3V - (33kohm//200kohm)*100µA = 0.47V still readable as a Low level.Second case: the 25µA source is connected.In this case, the IN will read Low if the OUT pin is HiZ: Imax = 3.3V/200kohm = 16,5µA < 25µAand High if the OUT pin is High: VIN = 3.3V - (33kohm//200kohm)*25µA = 2,6VThird case: the /CHG pin is HiZ.In this last case, IN will read High regardless of the state of the µP OUT pin, as only pull-ups are involved.So you can see that, by driving the OUT pin between High and HiZ and reading the IN pin, it's possible to detect the three states signaled by the /CHG pin.I hope that's clear enough!Edit: on second thought, using a suitable resistor and an analog input could be an easier way...e.g. with just a 68kohm pull up you'll have:100µA: about 0V25µA: 3.3-68k*25µ = 1.6V, square in the middle of the range.HiZ: 3.3V

author: gionag
author_rank: Newbie
timestamp: June 10, 2016, 09:04:27 pm
content: Fantastic !thanks, make perfectly sense.when investigating by myself I considered using an adc channel to detect different states, so you have confirmed me that is possible. I have to evalute if i prefer "wasting" two gpio or one adc channel.Thanks again for your support.
LTC4040 Charging problem - Page 1
Forum section: electronics / beginners

author: Najgel254
author_rank: Newbie
timestamp: January 04, 2020, 10:03:12 am
content: Hi all,i am building a LTC4040 backup system and i have a problem.Backup mode works fine, battery connected Li-Ion 18650 cell, boosting to 5V at output tested at 1A, working well. PFO LED is ON, other LEDS are OFF. When i connect input to LTC4040, 5V from my onboard buck converter (4A capability tested), LTC is still boosting from battery, PFO LED is OFF and all other LEDS are OFF. Load is powered from Li-Ion Cell, and power drawn from Buck is 0W. Charging is not hapenning too.In datasheet there is this part:"When the power-fail comparator detects that input power is available, the OVP chargepump starts to charge up the IGATE pin but the backupboost converter continues to deliver system load untilIGATE is approximately 8V. This ensures that the forwardconduction path through the external NFET pass transistors has been established. At this point, the backup boostgets deactivated and the charger turns back on to chargethe battery while the system load gets delivered directlyfrom the input to VSYS through the pass transistors."Page 16.I measured this, when LTC is in boost mode, PFO is ON ... Then i connect Input to the system, and measuring a IGATE pin to GND. There is sawtooth signal, from 0V to approx. 1V with frequency 5,7kHz. So i think LTC4040 cant charge Gate properly to 8V ? But why ? I tried 2 Mosfets ... One is PSMN6R0 and second is BSC0906 , same behaviour. When battery is disconnected and i connect input only, IGATE voltage is 8,7V and output is ON and powered from Input. But when battery is connected and then i connect input, IGATE voltage is stuck below 1V (oscillating).Schematic included. I tried changing Rprog(R35) to 2k2 to lower charging current but no change in behaviour.https://www.analog.com/media/en/technical-documentation/data-sheets/4040fb.pdfThank you.

author: Najgel254
author_rank: Newbie
timestamp: January 04, 2020, 10:33:17 pm
content: Topic Update:Now i tried other batteries, i connected a deep discharged good cell at BAT input. Datasheet says:When a battery charge cycle begins, the battery charger first determines if the battery is deeply discharged. Ifthe battery voltage is below VLOWBAT, typically 2.85V, anautomatic trickle charge feature sets the charge currentto 1/8th or 12.5% of the programmed value. To improvecharge current accuracy at this low level, the buck switching charger is turned off and a secondary linear chargeris used to deliver charge to the battery.After connecting Cell with voltage under 2,85V, i had 2,6V, LTC4040 started charging battery with current 113mA. Calculation says 12,5% from Iset = my case is 909mA. so 116mA.After battery reaches 2,85V charging stops, and Load is powered from battery ( i measured negative current) and power from input is 0W 0A.Someone who knows why my BUCK charger is not starting and charging properly?
LTDZ MAX2870 STM32 23.5-6000Mhz Signal Source Module  - Page 1
Forum section: electronics / beginners

author: FPSychotic
author_rank: Regular Contributor
timestamp: September 05, 2020, 10:01:55 am
content: Hi, I bought this signal source as I'm building a small and cheap 6Ghz capable lab to learn electronics.It has two outputs OutA+ OutA- ,could anyone please tell me for what they are, as I just can connect one of the two outputs into my others tools, power meter, digital attenuator, directional coupler, hackrf, adalm pluto,EMC probe,rf amplifier, they just can accept one input. What is the difference between both outputs and should I take some precaution to don't fry the hackrf (or other)input? In example use an attenuator.Basically, as my first project I want make vSWR meter and spectrum analyser with the SDRs my drone flying area, I think I have all needed to do it. I dont want transmit anything or make ham radio.This signal source is new, not reviews or info anywere, but there is a previous model with 4.4ghz instead 6ghz, Does someone knows of any pc software to control it? I know it works standalone, buy I know can be connected to a PC, which would help me to take contact with softwareThanks and sorry by my poor english[£36.58 28% OFF]Geekcreit® LTDZ MAX2870 STM32 23.5-6000Mhz Signal Source Module USB 5V Power Frequency and Sweep Modes Module Board from Electronic Components & Supplies on banggoodhttps://banggood.app.link/cKlQ0rVTw9

author: ebclr
author_rank: Super Contributor
timestamp: September 05, 2020, 02:36:44 pm
content: "The device also provides dual differential output drivers,which can be independently programmable to deliver-4dBm to +5dBm output power. Both outputs can bemuted by either software or hardware control."Those are differential lines, one is opposite to anotherhttps://datasheets.maximintegrated.com/en/ds/MAX2870.pdf

author: markl17@gmail.com
author_rank: Newbie
timestamp: March 11, 2022, 10:12:16 pm
content: is there a software for the max2870 generator thats sold by chines or is there a way to modify the step value from 1khz to 1hz
LTE Bands and Operating frequencies - how to pick? design considerations?  - Page 1
Forum section: electronics / beginners

author: roogadget
author_rank: Contributor
timestamp: October 11, 2018, 12:39:34 pm
content: I am playing with a CAT M1 module.Part of my design is using this device to send an SMS.I have to pick a band (because I'll do Pi-matching to filter the RF).How do I pick the best band? (My device is going to be low power.)E.g3GPP Band Transmit Receive UnitB1 1920~1980 2110~2170 MHzhttps://en.wikipedia.org/wiki/LTE_frequency_bands
LTPoE++ MOSFET Selection (Ideal Diode Bridge) - Page 1
Forum section: electronics / beginners

author: KKlouzal
author_rank: Newbie
timestamp: May 13, 2018, 08:34:58 am
content: Hello, I'm trying to select an appropriate MOSFET to use as an Ideal Diode Bridge for my LTPoE++ application.I need to support the maximum spec for LTPOE++ (90 watts).I'm using a Linear Technology LT4321 as the driver for my Ideal Diode Bridge.http://www.analog.com/media/en/technical-documentation/data-sheets/4321f.pdfTo save space on the PCB and reduce complexity these Quad N-Channel MOSFETs look very attractive.https://www.digikey.com/en/product-highlight/f/fairchild-semi/greenbridge-series-of-high-efficiency-bridge-rectifiersHowever i'm a beginner in the world of electrical engineering and I'm not quite sure if I can use these H-Bridge type fets for this application or not.I was also able to find this single mosfet from Nexperia but they aren't in stockhttps://assets.nexperia.com/documents/data-sheet/PSMN075-100MSE.pdfand I would like to use a single chip to save space and reduce complexity.The FDMQ8403 seems to be the best choice from what I can find, I'm just not sure about the H-Bridge, if anyone can clarify it would be really helpful.https://www.fairchildsemi.com/datasheets/FD/FDMQ8403.pdfI may just have to go with 8x of the TI CSD19538Q3Ahttp://www.ti.com/lit/ds/symlink/csd19538q3a.pdfAny recommendations would be greatly appreciated.Thank very much you for your time!
LTspice 12V SMPS flyback transformer ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 20, 2019, 08:37:22 pm
content: I made my 1st 1/2 of a 12V SMPS, using values from 1 whose bulk cap blew up, and blew the plastic case/glue apart.So I have the EMI stage, the single nmos, an inductor standing in as 1/2 the flyback. And I made a pnp multi-vibrator to stand in for the PWM chip.And it works 1st try !! Making circuits is fun.So what's the easy way to make a flyback transformer in LTspice that will output about 12.7V @1A ?

author: Buriedcode
author_rank: Super Contributor
timestamp: April 20, 2019, 11:05:03 pm
content: I'm not sure I fully understand. You made an actual circuit, that blew up?You mention you want a 12V output, but what is the input voltage? Mains? 48V ? 6v?A flyback is essentially a boost converter, with a coupled inductor (an inductor with more than one winding). If you're just playing around with an inductor, NMOS and multi-vibrator I'm not sure you fully understand how a flyback converter works. Start here:https://www.dos4ever.com/flyback/flyback.htmlIt is an excellent article explaining how the converter works, and why we select the parts and values we do. LTspice is also very handy for testing ideas, but the values (inductance, saturation current, DC resistance etc..) for a transformer will vary depending on the application, its not really about output voltage - strictly speaking it isn't really a transformer, because in a flyback converter it stores energy. It isn't like a mains AC transformer that has a rated output voltage for a given input voltage.

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 21, 2019, 01:34:21 am
content: I have a real SMPS that blew up. And I had drawn the circuit ages ago, so I put it in spice. It runs from sine wave 169V 60Hz, I'm using the resistor and cap values from the real SMPS. So I made the hot side, but I need a flyback transformer model.

author: mvs
author_rank: Frequent Contributor
timestamp: April 21, 2019, 10:30:02 am
content: Quote from: lordvader88 on April 21, 2019, 01:34:21 amPut two inductors (L1 and L2) on your schematic and couple them using SPICE directive K1 L1 L2 1

author: Buriedcode
author_rank: Super Contributor
timestamp: April 21, 2019, 06:25:24 pm
content: Quote from: lordvader88 on April 21, 2019, 01:34:21 amStart with a boost converter. I'm aware this will step up voltage, but once you have a boost converter, you can add a second winding to the inductor in LTspice as indicated bymvsabove. The turns ratio of the inductors is the square of the inductance. So if you want a 10:1 ratio, then primary should have 100 times the inductance of the secondary. The feedback comes from this secondary winding.

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 21, 2019, 10:38:17 pm
content: ok thanks
LTSpice 1/f Noise Simulations - Page 1
Forum section: electronics / beginners

author: fourierpwn
author_rank: Regular Contributor
timestamp: March 03, 2017, 11:46:28 pm
content: Hi again,I am trying to simulate 1/f noise in LTSpice for any nMOS or pMOS device. There is a noise simulation example given on LT's website however that involves an op-amp and I am unsure as to how to run such a simulation for a MOSFET device.Any help would be most appreciated

author: fourierpwn
author_rank: Regular Contributor
timestamp: March 04, 2017, 02:07:44 am
content: I thought I'd add some more information.Here is the example of the noise analysis example given by LT.Here is what I have done to translate this example over to a MOSFET.Note: The biasing of the MOSFET (VDS=1V and VGS=1V) has been changed from 0-20V with no difference in the simulation output. I have tried several different MOSFET devices to ensure that I had a model that included noise parameters too.Thoughts?

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: March 04, 2017, 02:56:12 am
content: Well, the first thing that strikes me is that Vout is clamped to 1.000000000000 V by Vds.Vds is mathematically noise-free so will exhibit none.Try sticking a resistor between the drain and Vds. 1 Ohm will do and you may multiply the output voltage by whatever actual resistance you may be interested in.Or you can monitor the drain noise current instead of its voltage.
LTspice - Page 1
Forum section: electronics / beginners

author: bill53
author_rank: Contributor
timestamp: July 04, 2025, 06:27:25 am
content: Hi All,I have attached (at lest hope I have) a very simple LTspice schematic. It consists of a voltage source with a 1 volt 1k Hz sinewave on an 80 volt offset. When I run this as a .tran the sinewave is distored. I've tryed this in both version 17 and 24 with the same result. Does anyone have any ideas what happening. Am I making some beginer mistake?CheersBill

author: iMo
author_rank: Super Contributor
timestamp: July 04, 2025, 07:08:32 am
content: ..looks like a bug in the "compression" setting.. disable it in the control panel..

author: Ian.M
author_rank: Super Contributor
timestamp: July 04, 2025, 07:21:41 am
content: ... or by adding the directive:Code:.opt plotwinsize=0to your schematic, which disables data compression for this specific sim, rather than globally, and also prevents the problem reoccurring when you share the sim with someone using default settings.
LTSpice and old models - Page 1
Forum section: electronics / beginners

author: Kirigozo
author_rank: Contributor
timestamp: October 10, 2013, 04:46:54 pm
content: Hi guys,I need to find a spice3 model of a BUZ71 mosfet. The only modules I've found are old and don't work in LTSpice. Does anyone know if a conversion program exists and where I might find it?The other option would be to use an equivalent device but the only xref site I found listed 576 devices as being the same. I think not. Does anyone know of a site that actually works?TIA

author: planet12
author_rank: Regular Contributor
timestamp: October 11, 2013, 12:24:55 am
content: Can you define what you mean by "don't work"?Most MOSFET models - the BUZ71 ones I've seen included - are sub circuit models, meaning you add the MOSFET symbol to your schematic, but then need to ctrl-right click the symbol and change the prefix to "X" then the value to the subcircuit model name as given on the model's .SUBCKT line.

author: planet12
author_rank: Regular Contributor
timestamp: October 11, 2013, 12:30:42 am
content: Oh, another point to watch out for - ltspice expects the pins in the order drain, gate, source. If the model you're using follows a different order, you'll have... fun.

author: Kirigozo
author_rank: Contributor
timestamp: October 11, 2013, 01:52:28 am
content: Thank you planet12 -- pin order was the problem.
LTSpice Bode plot analysis of discrete linear regulator - Page 1
Forum section: electronics / beginners

author: fmzambon
author_rank: Contributor
timestamp: August 19, 2021, 02:37:13 pm
content: Hello everyone,I'm working on a discrete high voltage linear regulator for my Nixie clock project.The purpose of the regulator is mainly to stabilize slow (< 1Hz) fluctuations in the transformed, rectified and filtered mains voltage to produce a relatively constant 180V output. The current requirements are very small, since I'm using 6 tiny B7977 tubes. Each one takes less than 1.1mA, so the regulator has to provide less than 6.5mA total. Ripple rejection is not a priority, even though it's a welcome side effectI built the circuit on a breadboard and it seems to work just fine, but I'm not 100% sure of the stability of the regulator. That's why I tried to do a Bode plot analysis to get an idea of what phase and gain margins I have.I did a search on the forums here (thread1thread2thread3thread4) and elsewhere on the internet, such as onAnalog's website, which seems to match what is in the LTSpice's FAQ section about getting a Bode plot for a SMPS (even though this is a linear regulator), and I got the attached plot.The question is: does this plot look correct? Or did I do anything wrong?The gain curve seems fine to me, but most plots that I've seen have the phase margin starts at >90° for very low frequencies and then generally descend below 0°. Here, on the other hand, it starts at 0°, climbs to almost 90° and then descends. Does this make sense?

author: Ian.M
author_rank: Super Contributor
timestamp: August 19, 2021, 03:14:58 pm
content: You may want to consider using Tien's method. Seehttps://sites.google.com/site/frankwiedmann/loopgainand in LTspice: examples\Educational\LoopGain2.ascN.B. as SPICE AC analysis uses an ideal linearized at its operation point model for all active components, you'll probably have to sweep the regulator's operating points for input voltage and for load current as they *WILL* affect the simulation's loop gain.

author: fmzambon
author_rank: Contributor
timestamp: August 20, 2021, 02:28:42 pm
content: Hello Ian.M,thank you for your suggestion.I started from that LTSpice example and progressively replaced the original circuit with my design. In the end I think that I got a sensible Bode plot with around 55° phase margin and 16dB gain margin at 190V input voltageAs for trying different input voltages and output loads, the output current will be pretty much constant in the intended application, so there's not much to test there. I tried different input voltages and the plot doesn't change all that much over the range of sensible input voltages. In fact at higher input voltages it looks like the phase margin increases to over 60°.The only thing I don't understand is that if I remove the Op-amp from the schematic, then the plot changes to something completely different, even though the Op-amp isn't connected to anything or mentioned in the expression that plots the Bode plotBest regards,Andrea
LTSpice Common emitter current gain problem? - Page 1
Forum section: electronics / beginners

author: renzoms
author_rank: Regular Contributor
timestamp: December 09, 2021, 06:21:55 pm
content: In LTSpice.I set up a npn linear amplifier.Changed the npn parameter "Bf" from 100 to 200.I thought Bf was Beta. The common emitter current gain of a (the) BJT.[following ie = ic + ib, and ib = ic/Beta, no early effect], I thought doubling Beta would half ib.I'm barely measuring a change. Idkw.Edit: So at Beta = 100. Everything lines up. ib = .023 and ic = 2.3, Then at Beta = 200 I get ib = .023 and ic = 3.3.?Ohit must be a saturation issuei guessbecause Vce goes low
LTSpice create complex PWM signal from MCU? - Page 1
Forum section: electronics / beginners

author: MathWizard
author_rank: Super Contributor
timestamp: July 21, 2020, 01:10:28 am
content: I want a 0-5V sqr.w that is on for 3us, off for 9us, then on for 15us, then off for 21us. Then loop that, that would do for my sim with an ADC and logic. The rise times are around 45nsSo how to I do that as a voltage source ?I could use some fast chips to switch between 2 regular PWM sources, but is there some direct way ? Or a chip in Ltspice that does this ?Thanks

author: Ian.M
author_rank: Super Contributor
timestamp: July 21, 2020, 02:02:06 am
content: A source set to:Code:PWL REPEAT FOREVER (0 0 +56n 5 3u 5 +56n 0 12u 0 +56n 5 27u 5 +56n 0 48u 0) ENDREPEATwill do what you want. +56n for the risetime because its 0% to 100% not the real-life standard of 10% to 90%, so 45n/0.8 gives close to the correct risetime. Enter the transition points relative to the first edge as time zero, rather than relative to the previous edge to avoid the need to subtract the risetime from the desired mark or space duration.Seehttp://ltwiki.org/?title=Undocumented_LTspice#Standard_Sourcesfor details of the REPEAT modifier to the PWL source. You can enter the times and voltages for a single cycle using the normal Advanced Source PWL editor, then manually edit in the REPEAT etc. Once you do so it disables the wizard so further edits must be done manually in the value string.'pre-cooked' sim of your waveform attached.Another option would be to use a repeated PWL file which you can generate programmatically or from a spreadsheet (e.g Excel). The plain repeated PWL list is more convenient if you want to parametrise the pulse timings so you can .step them in the sim.

author: MathWizard
author_rank: Super Contributor
timestamp: July 21, 2020, 02:25:33 am
content: Ok I'll try that, thanks.

author: langwadt
author_rank: Super Contributor
timestamp: July 21, 2020, 02:34:25 am
content: another option is to put multiple voltage sources in series, tweak the on/off times and delays to get your waveform

author: MathWizard
author_rank: Super Contributor
timestamp: July 21, 2020, 02:37:09 am
content: Another way is to see if I can program my AWG to do it, I'm sure it can, but I'll leave that till I get the sim working 1st, then try it on a breadboard.

author: SilverSolder
author_rank: Super Contributor
timestamp: July 21, 2020, 03:44:53 pm
content: Quote from: MathWizard on July 21, 2020, 02:37:09 amYou can export the waveform from LTSpice and use it in the AWG.You can also import waveforms you have sampled on your oscilloscope and use as a source in LTSpice.It really is a cool tool!
LTspice current flow directions - Page 1
Forum section: electronics / beginners

author: KM4FER
author_rank: Regular Contributor
timestamp: March 09, 2015, 05:47:37 pm
content: Now I understand that in circuit analysis you can pretty much choose any direction you want for current flow and the math works out as long as you keep the +'s and -'s correct but using certain conventions just seem more intuitive to me than others. Unfortunately LTspice doesn't seem to use nice conventions. For example:I've annotated the schematic with LTspice's choices for direction of current flow and they sure aren't the way I would have chosen. Why not? Well when you look at the graph you see that an increasing voltage results in a decreasing current through V1 and R3 but an increasing current through R1. This just seems to contradict Ohm's and Kirchoff's laws until you stop and think about it awhile.So, are LTspice's directions due to the way I drew the schematic or is there a way I can change them so the graph comes out the way I would expect with current following voltage?Thanks...earl...

author: MatthewEveritt
author_rank: Unknown
timestamp: March 09, 2015, 05:50:04 pm
content: I tend to be lazy and just plot the negative (right click on the signal name at the top of the plot and add a - to the front.)

author: c4757p
author_rank: Super Contributor
timestamp: March 09, 2015, 05:51:44 pm
content: Just rotate the resistors around.

author: IanB
author_rank: Super Contributor
timestamp: March 09, 2015, 05:53:32 pm
content: What happens if you flip R3 left to right on the schematic?

author: KM4FER
author_rank: Regular Contributor
timestamp: March 09, 2015, 07:01:50 pm
content: OK, testing shows that how you rotate/mirror the resistors does make a difference in how LTspice assigns current direction. I guess resistors must have a directional attribute after all ( joke, joke ).And I agree that putting the minus sign in the label of the waveform in the graph is the easiest way to change the looks of the graph.thanks everybody.
LTspice: when I turn a schematic into a subcircuit it behaves differently. Why? - Page 1
Forum section: electronics / beginners

author: czk9527
author_rank: Contributor
timestamp: November 02, 2016, 06:01:31 am
content: Hey guys, I ran into some trouble in LTSpice.Basically the problem is that the circuit behaves different if I make it into a custom symbol(subcircuit).I am simulating a TSMC018 CMOS op amp in ltspice, and need to test it using "gain of 2" non-inverting amplifier configuration. So I started by doing everything in one schematic sheet, which is shown in the attached "without using subcircuit.PNG". It worked fine as the simulation result shows, when the input is 100mV, the output is ~199.5mV.Then I made it into a custom symbol(subcircuit), as shown in the attached "subcircuit.PNG" and "symbol.PNG". Then I hooked it up with the external components (power supply, feedback resistors, biasing current etc). Simulated it and the output was off. It is shown in the attached "using subcircuit.PNG", when the input is 100mV, the output is ~194.8mV.I have no idea why this would happened. Can you guys please help me with that? Thanks.

author: Kalvin
author_rank: Super Contributor
timestamp: November 02, 2016, 09:32:44 am
content: Check the V2 and make it identical in both circuits. Otherwise the DC operating points may be different.

author: czk9527
author_rank: Contributor
timestamp: November 02, 2016, 09:45:46 am
content: Quote from: Kalvin on November 02, 2016, 09:32:44 amThanks for the reply. I went back to change both of the V2 to "none" and using the same ".dc V2 -0.45 0.45 0.001" for both of them. Still no luck.
LTspice D type flip flop...how to make it work - Page 1
Forum section: electronics / beginners

author: Faringdon
author_rank: Super Contributor
timestamp: November 23, 2021, 08:55:13 am
content: Hi,Do you know how to make the attached LTspice of a d type flip flop work?The output is just stuck high..woops sorry, it is working, please delete this post if you wish
LTspice dc sweep param  - Page 1
Forum section: electronics / beginners

author: OverMyHead
author_rank: Newbie
timestamp: April 13, 2025, 07:30:28 am
content: I'm trying to simulate two circuits simultaneously so I can probe their outputs on the same graph.Since each circuit requires an independent current source, I need to sweep both sources in parallel with same step.I attempted to use .dc + param as follow, but LTspice reports an error:Draft2.net(10): No such instance.Looks like LTspice dc sweep don't support param to be source?

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: April 13, 2025, 08:40:22 am
content: maybe this way:

author: Ian.M
author_rank: Super Contributor
timestamp: April 13, 2025, 10:34:54 am
content: A parametric sweep of the O.P's circuit:Code:.param I1=2m.step param I1 0 10m 0.001m.op(replacing the .dc sweep) works, but is horribly slow!Its vastly preferable to make the second source behavioural, and set its expression to echo the first, which can now be swept normally without any .params

author: OverMyHead
author_rank: Newbie
timestamp: April 14, 2025, 03:08:40 am
content: Quote from: Ian.M on April 13, 2025, 10:34:54 amIt is slow but works, thanks!Yes, probably this is an unusual case—I just want to explore whether there’s a way to achieve it.

author: Ian.M
author_rank: Super Contributor
timestamp: April 14, 2025, 11:24:43 am
content: A third approach is to add a seperate controlling source. If you make it a voltage source, with internal resistance of -1 ohm (yes, Negative resistance!), you can short-circuit it and the current through it will be proportional to the voltage at 1A/V and of the same sign. Ii can then be used (by name) as the control source for linear current dependent voltage (H) and Current (F) sources. It can also be used to control Current controlled Switches.
LTSpice: differences running frequency and bode plot - Page 1
Forum section: electronics / beginners

author: eTobey
author_rank: Super Contributor
timestamp: January 09, 2024, 11:11:27 pm
content: Hi,im learning to use LT spice, and i came across something which is not exactly right.In the bode plot, i see a gain to 455mV at 500kHz (red line), but when i actually run this frequency, it goes only to 450mV. Did i do something wrong, or is this some calculation error?

author: Benta
author_rank: Super Contributor
timestamp: January 09, 2024, 11:35:55 pm
content: If the red sine is 500 kHz, then yes, peak amplitude is 450 mV.But your Bode plot peaks at around 540 kHz. At 500 kHz it's also 450 mV.

author: eTobey
author_rank: Super Contributor
timestamp: January 09, 2024, 11:58:09 pm
content: I am running at 500khz, and that is not the peak.

author: Benta
author_rank: Super Contributor
timestamp: January 10, 2024, 12:07:15 am
content: Your 500 kHz point is here:

author: eTobey
author_rank: Super Contributor
timestamp: January 10, 2024, 06:35:48 am
content: Yes, but this is not the peak in the bode plot. Also its not 450mV if you look carefully. I made another plot to verify.

author: Benta
author_rank: Super Contributor
timestamp: January 10, 2024, 12:11:02 pm
content: Quote from: eTobey on January 10, 2024, 06:35:48 amWut? I read exactly 450 mV at 500 kHz.Seems you don't understand what a Bode plot shows.PS: your plot doesn't display, the file is probably too large.

author: eTobey
author_rank: Super Contributor
timestamp: January 10, 2024, 04:48:01 pm
content: I readded the screenshot.

author: Benta
author_rank: Super Contributor
timestamp: January 10, 2024, 07:17:52 pm
content: Well, the Bode plot shows ~455 mV.Your sine simulation has much lower resolution and too few simulation steps (obvious from the piecewise curve fitting).Very probable that the sine simulation will also show 455 mV if you increase number of steps.
LTspice FFT on current waveform? - Page 1
Forum section: electronics / beginners

author: questron
author_rank: Regular Contributor
timestamp: November 07, 2014, 05:36:02 am
content: how could i do an FFT on a current waveform in LTspice?i did a .four i(lc(Q1)) for example, it didn't work.i just want the THD number on an AC current, does this make sense, doable in LTspice, what's the correct syntax for it?googling didn't yield any results.tks!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 07, 2014, 07:47:53 am
content: If nothing else, do the .tran simulation, plot the waveform, then View / FFT.Tim

author: macboy
author_rank: Super Contributor
timestamp: November 07, 2014, 03:27:15 pm
content: Quote from: T3sl4co1l on November 07, 2014, 07:47:53 amThis is the way to get a graphical result. To get a tabulated list of amplitudes of harmonics, use ".four" directive. The OP is missing the frequency from the .four directive. This should work (for 1 kHz):.four 1kHz Ic(Q1)Also ensure that the simulation time is an exact multiple of the period of the fundamental, in order to improve the FFT result (to avoid a slant of the noise floor towards DC). Also add this directive:.option plotwinsize=0...which will disable compression, which would otherwise increase distortion due to reduced precision in calculations.

author: questron
author_rank: Regular Contributor
timestamp: November 07, 2014, 04:52:59 pm
content: Quote from: T3sl4co1l on November 07, 2014, 07:47:53 amdid that and got a rough idea about its distortion, thank you Tim for the help!

author: questron
author_rank: Regular Contributor
timestamp: November 07, 2014, 04:59:03 pm
content: Quote from: macboy on November 07, 2014, 03:27:15 pmthat worked beautifully, thanks a lot macboy!didn't know the impact on slanting noise floor before, very nice and useful tip!all is much appreciated!
ltspice - getting "Unknown subcircuit" when using a .model directive  - Page 1
Forum section: electronics / beginners

author: ledtester
author_rank: Super Contributor
timestamp: January 30, 2016, 06:22:22 am
content: I'm trying to use a .model directive in my schematic, but I'm getting an "Unknown subcircuit" error when I try to run the simulation.I can get it to work if I use a .subckt directive instead. I've attached the ltspice file (it's a very simple circuit.)What am I doing wrong?Here is the complete .asc file:Version 4SHEET 1 1520 2404WIRE -560 -32 -688 -32WIRE -448 -32 -560 -32WIRE -448 80 -448 48WIRE -688 96 -688 -32WIRE -560 160 -560 -32WIRE -496 160 -560 160WIRE -688 224 -688 176WIRE -560 224 -688 224WIRE -448 224 -448 176WIRE -448 224 -560 224WIRE -560 240 -560 224FLAG -560 240 0SYMBOL nmos -496 80 R0SYMATTR InstName M1SYMATTR Value 2N9999SYMATTR Prefix XSYMBOL voltage -688 80 R0WINDOW 123 0 0 Left 2WINDOW 39 0 0 Left 2SYMATTR InstName V1SYMATTR Value 5SYMBOL res -464 -48 R0SYMATTR InstName R1SYMATTR Value 1kTEXT -688 296 Left 2 !.tran 0 0.001 0 1uTEXT -688 360 Left 2 !.model 2N9999 VDMOS(Rg=3 Vto=1.6 Rd=0 Rs=.75 Rb=.14 Kp=.17 mtriode=1.25 Cgdmax=80p Cgdmin=12p Cgs=50p Cjo=50p Is=.04p mfg=Fairchild Vds=60 Ron=2 Qg=1.5n)

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 31, 2016, 04:16:47 am
content: I tried for awhile with no luck myself so I decided to look for the spice line itself. Minus the 2N9999 part, the following line is exact and I found ithereCode:.model 2N7002 VDMOS(Rg=3 Vto=1.6 Rd=0 Rs=.75 Rb=.14 Kp=.17 mtriode=1.25 Cgdmax=80p Cgdmin=12p Cgs=50p Cjo=50p Is=.04p mfg=Fairchild Vds=60 Ron=2 Qg=1.5n)Seeing that, I added a 2N7002 to the simulation and it works though I don't understand what you're trying to achieve with it.Edit: just for fun, here's the models from Fairchild.

author: bson
author_rank: Unknown
timestamp: February 01, 2016, 12:57:12 am
content: Get rid of the "prefix x".

author: eetech00
author_rank: Regular Contributor
timestamp: February 01, 2016, 02:17:25 pm
content: Delete the NMOS device then add it back inIf you change the prefix to "X", LTspice searches for a .subckt definition.Since you are using a .model statement, do not change the prefix to "X".

author: ledtester
author_rank: Super Contributor
timestamp: February 11, 2016, 05:16:40 pm
content: Thanks everyone - blanking out the PREFIX for the device worked.I've had a lot of trouble modifying the ltspice lib files to include the 2n7000 definition, so I wanted to figure out how to hard code a device definition into the schematic file using a .model directive.
LTspice help - transformerless power supply simulation - Page 1
Forum section: electronics / beginners

author: RicardoATB
author_rank: Newbie
timestamp: February 08, 2011, 08:48:07 pm
content: Hi!I'm new to LTspice simulations and I would like to construct the following "Capacitive Transformerless Power Supply- App. Notehere", but when I run the simulation, I get onnet1the same voltage ofV1and not something like5 VDC. What am I doing wrong?Thanks in advance and Long Live David Jones

author: RicardoATB
author_rank: Newbie
timestamp: February 08, 2011, 08:57:38 pm
content: Herefollows my LTspice file.

author: Unknown
author_rank: Unknown
timestamp: February 08, 2011, 09:24:32 pm
content: If you move the ground node to the same location as in the appnote, or plot V(net1) - V(n003), you'll see the results you'd expect: the zener voltage minus the drop over D2.If you want to build this, you must consider the whole circuit as dangerous mains, since the caps provide no galvanic isolation, and are probably not rated for line filters (X/Y), so they may be destroyed (or fail shorted) by transients.

author: RicardoATB
author_rank: Newbie
timestamp: February 08, 2011, 09:58:39 pm
content: Thank you very muchalm! It worked!Thank you too for warning me about the risks, as says theMicrochip Application Note, I'll use a fuse and other security considerations when I build it.

author: Zero999
author_rank: Super Contributor
timestamp: February 10, 2011, 06:10:07 pm
content: There needs to be a bleeder resistor (about 1M) across C1 to prevent someone from getting a shock when the plug is removed.What's the supply voltage? LTSpice uses the peak voltage so 110V is only equivalent to 78V RMS, you need to enter 155.6V for 110VAC.