hybridfree/eevblog-posts huggingface dataset:
Transimpedance Amplifier Layout Design  - Page 1
Forum section: electronics / projects

author: Arsh ahmad
author_rank: Regular Contributor
timestamp: May 21, 2025, 07:25:57 am
content: I am working on a Transimpedance Amplifier using OPA847, to operate this for 30+Mhz, I have set the feedback gain to 2k , also cf to 0.5pF, is it okay to put a feedback capacitor of 0.47pF or a parasitic capacitance will do. I also want to have a basic review of the layout. I have attached images of schematic as well as layout section.

author: Terry Bites
author_rank: Super Contributor
timestamp: May 21, 2025, 01:32:39 pm
content: The feedback capacitor required will depend on the capacitance seen at the TIA input, source+wiring+stray etc.That needs to be tightly controlled if you want accurate compensation.So, the wrong pcb stray could ruin your day whether at the input or in the feedback.

author: Arsh ahmad
author_rank: Regular Contributor
timestamp: May 22, 2025, 08:11:58 am
content: Total Input capacitance is 15pF

author: Terry Bites
author_rank: Super Contributor
timestamp: May 27, 2025, 07:28:52 pm
content: Use one of the TIA deisgn tools.AD has its "photodiode amplifier wizard"and TI has something similar I think.Others I'm sure

author: TimFox
author_rank: Super Contributor
timestamp: May 27, 2025, 07:56:44 pm
content: You might consider adding a trimmer capacitor to the feedback network to achieve a good pulse shape, although they can be large compared with a normal SMD capacitor.For example:https://www.mouser.com/ProductDetail/Knowles-Johanson-Manufacturing/9402-0?qs=lc2O%252BfHJPVaDtlG1ZRRjOw%3D%3D
Transimpedance amplifier noise calculation - Page 1
Forum section: electronics / projects

author: arivalagan13
author_rank: Contributor
timestamp: April 20, 2021, 05:19:17 am
content: Hi allI want to calculate the output noise voltage at the output of an op amp-based transimpedance amplifier. Here I've attached a file where I did an example calculation. Can somebody please tell me whether my calculations are correct???RegardsM. A

author: Kleinstein
author_rank: Super Contributor
timestamp: April 20, 2021, 07:16:46 am
content: The 20*log (1+32p/1p) part is not correct. This is somewhat mixing with the dB scale. However the numerical result for 20*log .. is not far off the corret factor without the 20*log part. So by lucky coincidence the mistake does not change much.The calculation assumes that the ouput is sampled not much faster than some 50 kHz, so it does not include much higher frequency noise. Chances are this is OK for the application.There would be a small contribution from low frequency 1/f noise of the OP. So kind of add the 0.1-10 Hz RMS noise to the final result. This would be negligible in this case with high TIA gain and high BW, but could be an issue in other cases.

author: awallin
author_rank: Frequent Contributor
timestamp: April 27, 2021, 03:16:16 pm
content: FWIW I wrote some python scripts that predict dark-noise and frequency response for simple one op-amp transimpedance designs.there's also a few comparisons to real-world measurements in the repo:https://github.com/aewallin/TIASimif there's something not clear please ask or submit a github issue and I may improve the documentation.HTH

author: graybeard
author_rank: Frequent Contributor
timestamp: April 29, 2021, 06:14:05 am
content: The temperature for the resistor is Kelvin, not Centigradep.s. I still use mhos for conductance as well!

author: harerod
author_rank: Frequent Contributor
timestamp: April 29, 2021, 07:56:11 am
content: Quote from: graybeard on April 29, 2021, 06:14:05 amYou Americans surely have a hard time with units not statute, ey? YMMD.
Transimpedance BJT Amplifier Design - Page 1
Forum section: electronics / projects

author: JakubTrybek
author_rank: Newbie
timestamp: November 07, 2024, 01:16:15 pm
content: Hi all, i have been tasked to design a Transimpedance amplifier using BJT'S, In this case a CE - CC stage amplifier. I have shown the circuit and H parameter below,Im struggling in the derivation of the gain which is needed to verify my multisim results. If anyone could give any support i would greatly appreciate it.I am particularly struggling with including the Feedback resistor, the value has been calculated in order to suit my bandwidth of 1Mhz.

author: Marco
author_rank: Super Contributor
timestamp: November 07, 2024, 04:33:21 pm
content: If it's a little lower than 50k I'd just believe the sim and move on :p

author: TimFox
author_rank: Super Contributor
timestamp: November 07, 2024, 05:13:54 pm
content: The circuit for the CC output stage doesn’t look right: the input impedance will be higher than that of the CE input stage, but you have them both athie.I would start with transistor models based on transconductance, rather than current gain.

author: youngda9
author_rank: Regular Contributor
timestamp: November 07, 2024, 06:40:31 pm
content: Is this the place for college kids to come get help with their homework now?
Transimpedance converter / amplifier - Page 1
Forum section: electronics / projects

author: ACertainIdioticEngineer
author_rank: Newbie
timestamp: August 22, 2020, 08:55:36 pm
content: Hi first post here in this forum, sorry if this already existed on the forum, didn't find any tho.Currently trying to "design" a circuit which can convert a 4 - 20 mA sensor into a voltage which i then can read out with the Arduino. The problem lies in how precise it has to be. The resolution of the laser is 0,2 mA/mm in 16um steps. So this circuit should just convert the current of a 16um step into 4,88mV while being stable enought that the ADC doesn't change the LSB when on the same point. The Circuit i built should work however when i meassure the virtual ground on the OPAmp I get a voltage of -12V and the current to the sensor is -1,7mA. The Sensor can drive up to 300and if i meassure the laser without the OPAmp it works just fine. The 1kresistor represents the next load for an inverting OPAmp. The pins should be connected correctly since i rebuild it 3 times and got the same error each time. Powering it from an external 12V power supply (~13,4VDC). The Laser is a Z4M-W100RA

author: KT88
author_rank: Frequent Contributor
timestamp: August 22, 2020, 09:43:19 pm
content: The Z4M-W100RA features a current source and the TIA inverts the voltage. This circiut would require a negative supply and another inverer to get a positive output for your Arduino...You could use just an appropriate shunt that feeds directly into the Arduino. Maybe a buffer witht the possibility to cancel the 4mA related offset. Some overvoltage protection won't be bad as well.

author: ACertainIdioticEngineer
author_rank: Newbie
timestamp: August 22, 2020, 10:30:06 pm
content: thanks will try it out... forgeting the negativew supply rail...
transimpedance current to voltage converter input protection. - Page 1
Forum section: electronics / projects

author: hemnath
author_rank: Newbie
timestamp: June 13, 2017, 03:25:33 am
content: I am trying to use feedback ammeter for current to voltage conversion. Please find the attached circuit.I am worrying about the input protection circuit. Please help in choosing the components for input protection. Also if the terminals are accidentally connected to 230V AC, it should protect the circuit.Please help.

author: David Hess
author_rank: Super Contributor
timestamp: June 13, 2017, 12:26:03 pm
content: How much input series resistance or voltage drop can you tolerate?I might use a small high voltage incandescent bulb instead of a PTC for faster response.In a high performance application, I would consider using depletion mode MOSFETs for high voltage current limiting.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 13, 2017, 08:27:27 pm
content: Why would you put voltage-dropping elements in series with a current input? What's wrong with a back-to-back pair of bigass diodes?Tim

author: David Hess
author_rank: Super Contributor
timestamp: June 14, 2017, 12:57:50 am
content: Actually there is a way to do with effectively zero input resistance; I just had to remember it. Ohms converters place the input protection *between* the summing node and the amplifier input.The input impedance of the operational amplifier inputs is very high so they can tolerate large series resistance between the inputs and the summing node. The input shunt protection then goes directly at the inputs and the output of the operational amplifier and the measured current goes into the summing node.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 14, 2017, 05:15:42 am
content: Quote from: David Hess on June 14, 2017, 12:57:50 am^^^Tim

author: hemnath
author_rank: Newbie
timestamp: June 14, 2017, 06:53:45 am
content: Quote from: David Hess on June 14, 2017, 12:57:50 amThank you. Can you show me the handsketch and how to calculate the resistor value?I found this diagram in the keithley notes. Please check it

author: hemnath
author_rank: Newbie
timestamp: June 15, 2017, 03:22:49 am
content: any help please.

author: hemnath
author_rank: Newbie
timestamp: June 19, 2017, 03:42:01 am
content: If i put a resistor as shown in the fig, it won't change the current flow? any suggestions
Transistor as remote power switch? - Page 1
Forum section: electronics / projects

author: Guitar42
author_rank: Contributor
timestamp: February 15, 2019, 08:33:52 pm
content: I have a design I'm working on that consists of two PCBs that are separated by 8 inches or so. The main board has a microcontroller, battery charger IC, and other stuff on it. The other board just has a few LEDs, momentary switches, and a slide switch for power. I've got the main power running from the main board to the daughter board, thru the switch, and then back to the main board. I'd like to not run main power to this daughter board, but I'd like to keep the power switch on the daughter board. Is there a way to use a transistor on the main board that is controlled by the slide switch on the daughter board to turn on and off main power? Ideally I'd prefer to run as little power to the daughter board as possible as I'm concerned about EMI. I just don't have much experience with transistors as switches.

author: Zero999
author_rank: Super Contributor
timestamp: February 15, 2019, 11:50:09 pm
content: Yes, a transistor is a possibility. Do you want to switch the high or the low side?How about using a relay?

author: Guitar42
author_rank: Contributor
timestamp: February 16, 2019, 12:02:05 am
content: Probably better to switch the high side, but I don't think it matters. I'd rather use a transistor than a relay mainly for space and cost reasons.

author: Zero999
author_rank: Super Contributor
timestamp: February 16, 2019, 12:29:12 am
content: What current and voltage?Are there any other signals going between the two boards?

author: Guitar42
author_rank: Contributor
timestamp: February 16, 2019, 12:49:40 am
content: The board is running of a 3.7v lithium battery, about 800 mA. There are a few momentary switches on the second board and a few LEDs, all connected to a ATMEGA32U4.

author: Zero999
author_rank: Super Contributor
timestamp: February 16, 2019, 07:47:40 pm
content: I'd go for a PNP BJT with lots of gain.https://www.diodes.com/assets/Datasheets/ZTX788B.pdfhttps://www.diodes.com/assets/Datasheets/ds31618.pdfA P-channel MOSFET is another possibility but make sure you get one which can pass the desired current, with a gate voltage of under 3V. I had a quick flick through Mouser and found a couple:https://www2.mouser.com/datasheet/2/308/NTR3A052PZ-D-1219532.pdfhttps://www2.mouser.com/datasheet/2/427/72023-244672.pdf

author: Guitar42
author_rank: Contributor
timestamp: February 16, 2019, 07:54:21 pm
content: Cool, thanks! I was actually just looking at EEVBlog #262 and thinking that the schematic at the beginning of the video might fit my needs. I have several momentary switches near the power switch and I'd rather not risk turning the device off on accident so I'm going to try it with the slide switch I currently have. Do you recommend any of those 4 parts in particular for this application? The NTR3A052PZ looks like it should be able to handle the load and voltage.
Transistor computer and 8/16BIT computer dev board. - Page 1
Forum section: electronics / projects

author: rickey1990
author_rank: Regular Contributor
timestamp: December 02, 2015, 01:51:17 am
content: Recently iv been working on a basic transistor computer, the 2 board's comprise of a full adder and a subtracter. The boards need labeling abit better but heres a basic idea of the layouts.Also after watching the new steve jobs movie, Me and brother got into a dissussion about 8 and 16 bit computers. Being born in 1990 i had to look for old scems, to see how they worked, i then decieded to get some chips, i ordered enouth parts for 6 different computers using 5 different cpu's, mid 70s to mid 80's. including a some old ussr chips and a RCA 1802, Used in the Galileo spacecraft which looked cool.With all these chips and them being different sizes, I wanted a test bed to prototype the designs on. i could have used a breadboard but hay it doesnt cost much to print a pcb. should have the gerbers next week. Heres a crude pic. The lines show the way the tabs are connected, Only afew connections have been drawn on but all are connected.MY PROJECTShttp://beambuilder.blogspot.co.uk/2015/04/my-projects.html

author: pmbrunelle
author_rank: Regular Contributor
timestamp: December 02, 2015, 03:29:31 am
content: I kind of like the idea of those breadboard-facsimile PCBs. I didn't know they existed, so I found some here:https://www.adafruit.com/products/1606They will make your project more permanent, but without changing the basic layout, so any testing you do on the breadboard is probably representative of the function of the circuit on the breadboard-facsimile PCB.Wait, I don't understand. The purple PCBs, are they meant to plug into a breadboard? I would see that as an interesting way to construct a DIY computer. Instead of DIP chips, use custom-made PCBs (with your discrete stuff) with two rows of pins, and plug them into the breadboards.
Transistor current source (sink), high current, low dropout - Page 1
Forum section: electronics / projects

author: 741
author_rank: Frequent Contributor
timestamp: June 20, 2018, 08:29:11 am
content: I'd like to realise a fast acting current source. It might well be saturated at times, but must recover ASAP.About 10A, about 30V max.For reasons of speed (esp saturation recovery), stability and simpler power supply, I assumed a standard NPN current sink with a set voltage on the base, then (minus a vbe drop) across the sense resistor on the emitter.If the equation re ~= 25/(1000.I) is about right, I guess the sense resistor has to be at least 10 times that. re = 0.0025 Ohms (2.5 mOhms) at 10A; RE = 25mOhm, sense-resistor dropout = 0.25VBut 0.25 is small compared with a hard-to-define Vbe, maybe 0.7..0.9V at this current, so its rather inaccurate. Normally, when sense dropout is no concern, and lower currents, Vbe inaccuracies can be brushed aside.
Transistor Curve Tracing Shows Weird Scope Display - Page 1
Forum section: electronics / projects

author: RonFred2
author_rank: Contributor
timestamp: May 01, 2021, 09:19:24 pm
content: I recently crafted a transistor curve tracer with my Oscilloscope and Arbitrary Waveform Generator. Most BJT Si transistors show typical/normal traces but one device undertest produces abnormal trace when collector-emitter voltage (Vce) goes higher than about 6 Volts.Does anyone know what is the cause of this abnormal trace?I present a few images below showing my test setup, a good trace, and the weird trace.http://www.biophysicslab.com/2021/04/27/testing_transistor_hfe/#measure-hfe-using-an-oscilloscope-and-arbitrary-waveform-generator-awg

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 01, 2021, 11:15:21 pm
content: I suppose it's not inverted as hFE looks reasonable. Just defective then?Negative resistance is normal avalanche operation -- but this normally occurs between Vceo and Vcbo, over 60V for 2N3906.Tim

author: RonFred2
author_rank: Contributor
timestamp: May 05, 2021, 01:30:08 am
content: Someone on another forum had this to say about this circuit and transistor behavior, with one other person agreeing...QuoteI thought this contribution may help others who look at this issue as well.Thank you all for looking at my forum post here.
transistor equivalent table - Page 1
Forum section: electronics / projects

author: 1thierry
author_rank: Newbie
timestamp: January 31, 2022, 02:58:15 pm
content: Hi everyone,I am looking for the replacement part of SPF3043...and i did not find a equivalent device.Is there somewhere on the web a big data sheet with equivalent discontinued part?

author: w2aew
author_rank: Super Contributor
timestamp: January 31, 2022, 04:40:39 pm
content: Sirenza Microdevices (the manufacturer) was acquired by Qorvo in 2008 or so. Since wideband pHEMT GaAs FETs are not as popular and widespread as something like a 2N2222A, you're likely not going to find a direct replacement. Your first stop should be to contact the applications engineers at Qorvo to see if they've continued the part (under their own part numbering scheme), or can suggest a replacement.
transistor for high side load switch: turning off chips 3.3V ~100mA - Page 1
Forum section: electronics / projects

author: djacobow
author_rank: Super Contributor
timestamp: August 14, 2014, 02:51:12 am
content: I am working on a design in which I'd like to switch off all power to a subset of chips on the board. Current consumption would be well under 100mA and this is a 3.3V design.I'm looking at FDN306P ($0.21 qty 100), PMK50XP ($0.29 qty 100), etc.Anybody have a favorite?Switching characteristics are not important as this will be on or off for very long periods. I am concerned about on state resistance especially as the battery starts to fade and both Vds and Vgs start to go down.

author: Richard Head
author_rank: Frequent Contributor
timestamp: August 14, 2014, 05:55:06 am
content: Those devices you have suggested will work perfectly, but they are pricey compared to bipolars.If it's not a cost sensitive design then by all means go for it. If it's a high volume product where every cent counts then I would be inclined to consider a PNP bipolar in a SOT-23 package.The PNP bipolar should be a lot cheaper.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2014, 06:37:15 am
content: If you're pressed for pennies, PNP might save you a few. But you'll have to be miserly with the base current to keep battery life from being much worse. Are those loads always at 100mA, or do they vary? You generally size the base current for the worst case, and eat the excess as wasted efficiency at light load.Oh, and don't forget to set all the interconnections going to those devices as 'Z' (tristate / input mode) or '0' (logic low) so you don't phantom-power them from the logic.Tim

author: Precipice
author_rank: Frequent Contributor
timestamp: August 14, 2014, 06:57:51 am
content: When you say current is well under 100mA, is it far enough under to just drive from an IO pin? Two IO pins paralleled up and driven very carefully?(If you're in a low power environment, take care about charging the decouplers on your switched side.)

author: djacobow
author_rank: Super Contributor
timestamp: August 14, 2014, 08:05:04 am
content: Quote from: Precipice on August 14, 2014, 06:57:51 amNah, it's primarily a bluetooth radio that peaks at 75mA, normal xmit is 45-50mA and quiescently should be much less.I will think about the BJT. Thanks for the advice, guys.Will have to remember not to drive power through the inputs. I've seen it a zillion times. Chips can work all day through "magic."
Transistor manufacturer logo identification help please - Page 1
Forum section: electronics / projects

author: bd139
author_rank: Super Contributor
timestamp: March 12, 2019, 04:41:46 pm
content: Anyone know who made this? Don't recognise the logo.Is a 2N3053

author: RES
author_rank: Regular Contributor
timestamp: March 12, 2019, 05:42:31 pm
content: https://www.elnec.com/en/support/ic-logos/?method=logo

author: bd139
author_rank: Super Contributor
timestamp: March 12, 2019, 06:06:16 pm
content: Couldn't see it on any of them.

author: jaycee
author_rank: Regular Contributor
timestamp: March 12, 2019, 06:10:43 pm
content: SemeLAB

author: Jokerz
author_rank: Newbie
timestamp: January 29, 2020, 08:11:41 am
content: Can someone please help me identify this manufacturer logo?

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 29, 2020, 11:58:41 am
content: This looks close:

author: Jokerz
author_rank: Newbie
timestamp: January 29, 2020, 12:12:50 pm
content: Mospec has a black thick logo. Have them somewhere.

author: RadioNZ
author_rank: Newbie
timestamp: March 31, 2022, 01:01:56 am
content: I have just found a 2N3055 with the same logo.Has anyone been able to determine who made these?

author: amyk
author_rank: Super Contributor
timestamp: March 31, 2022, 04:38:14 am
content: Magnatec (appears to be long defunct.) Example of one of their datasheets showing the logo:https://web.archive.org/web/20080528085310/http://www.magnatec-uk.co.uk/pdf/magnatec/BUZ900.pdf

author: kontitu
author_rank: Newbie
timestamp: December 07, 2022, 11:40:00 am
content: I have a similar challenge on my hands. Would any of you recognize this IC?

author: amyk
author_rank: Super Contributor
timestamp: December 08, 2022, 02:59:16 am
content: You should start a new topic for this, but what does it say? 20CM L604?
Transistor N° - Page 1
Forum section: electronics / projects

author: yalect
author_rank: Regular Contributor
timestamp: June 14, 2020, 08:43:06 am
content: Hello,I would like to ask you about this transistors reference and maybe the manufacture fabricated.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 14, 2020, 09:12:16 am
content: TO-220: STP60NF03Lhttps://www.st.com/resource/en/datasheet/cd00001901.pdfTO-92:https://alltransistors.com/transistor.php?transistor=62095S8550, PNP, unknown manufacturer. Jellybean, many sources.Tim

author: yalect
author_rank: Regular Contributor
timestamp: June 14, 2020, 06:32:21 pm
content: Thank you,and this small transistor

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 15, 2020, 01:36:37 am
content: http://www.s-manuals.com/smd/3dThis site and a few others are the first place to look for small SMT codes.Tim

author: yalect
author_rank: Regular Contributor
timestamp: June 15, 2020, 10:54:08 am
content: thank youSo, it'sMMBTA44npntransistor, there are five manufacturers.Greeting
Transistor question - Page 1
Forum section: electronics / projects

author: Unknown
author_rank: Unknown
timestamp: October 04, 2013, 01:32:18 pm
content: Hola,I have a project which has two 450V 10A NPN transistors in the circuit and I haven't found a suitable data-sheet.One is stuffed. Which is being changed.On a diode test, the other reads 0.385 and 0.502 when measured, which seems to me to be a large difference.So, the question is,is the transistor still within functionable parameters with those readings, or could it possibly fail alongside a new partner?Cheers.

author: Alana
author_rank: Frequent Contributor
timestamp: October 04, 2013, 01:38:33 pm
content: First - do you mesure it desoldered completely?

author: Unknown
author_rank: Unknown
timestamp: October 04, 2013, 01:45:21 pm
content: Hi,Yeah, desoldered completely. On the bench.

author: Unknown
author_rank: Unknown
timestamp: October 04, 2013, 02:07:15 pm
content: The reason I ask is that if those readings were on, say a BC547, then I would consider it failing...and the high voltage, high amperage, transistor field is not my comfort zone.I would imagine it would work, but unless someone knows different, then I'm not mad on having such an imbalance in the transistors, as I am fairly sure that the new transistor (C4237) will read 0.600+ on from B to both C & E pins.

author: Alana
author_rank: Frequent Contributor
timestamp: October 04, 2013, 02:17:58 pm
content: I'd do the very same thing - if BE and BC are so different its usually faulty. To be sure try to turn a light blub with that transistor - if it works it may be ok but i doubt that.

author: Unknown
author_rank: Unknown
timestamp: October 04, 2013, 07:59:34 pm
content: Update...When tested in the shop, one new 2S C4237 tested 0.548 & 0.445 and another 0.502 & 0.435, so I decided to take a chance and only buy one, the one which tested closest to the existing transistor (which is actually testing 0.514 & 0.397).When I saw that the brand new ones also have a large difference in measurement, I realised that perhaps the original transistor is not as bad as imagined?That coupled with the fact that to install the 2SC4237 entails drilling and a bit of open-heart surgery,it seemed prudent to start with the one that is 100% failed.

author: Paul Price
author_rank: Super Contributor
timestamp: October 04, 2013, 09:17:03 pm
content: With the majority of bjt's there is most common a difference between c-e and b-e readings, and this reading varies with the make and model of meter making this measurement.
Transistor selection for simple series regulator - Page 1
Forum section: electronics / projects

author: hkBattousai
author_rank: Regular Contributor
timestamp: July 04, 2014, 01:34:47 pm
content: I'm designing a simple series linear voltage regulator as seen in the schematic below. I'm concerned about what should power rating of Q1 be. I understand that Q2 (BD135) will have a large voltage drop, and heat up profusely; so it must be cooled down. But, what about Q1? How much voltage drop will it have? Can I use a tiny cheap SOT-23 package for it, or should it also be a big bulky power transistor?My confusion arises from not being able to guess Izand I1currents. What should be the value of R1 in order to minimize the total power loss on R1 and Q1?Note: Load current will be 200mA at most. Output voltage value isn't necessary to be precise; it may vary +/-1V.

author: dannyf
author_rank: Super Contributor
timestamp: July 04, 2014, 01:45:41 pm
content: The voltage drop over Q1 is 24 - 17.3v = 7v.The maximum current on Q2 is 200ma. Check the datasheet for Q2's minimum beta but I would use 20. That means base current of 10ma.So power dissipation if 70mw. Double that to be sure, a 150mw dissipation.

author: David Hess
author_rank: Super Contributor
timestamp: July 04, 2014, 01:57:21 pm
content: The power dissipation of Q1 will be about the power dissipation of Q2 divided by the current gain of Q2. That will probably end up on the order of 1.5 watts for Q2 and 40 milliwatts for Q1 worst case.R1 needs to supply enough current for both the worst case base drive of Q1, maybe 125 microamps, and for the zener diode. 10k seems high to me and I would probably go with 2.2k or so.

author: mij59
author_rank: Frequent Contributor
timestamp: July 04, 2014, 02:01:36 pm
content: The transistors T1 and T2 configured as emitter followers, I1 will be very low , 100 uA or so.The zenerdiode Z1 needs a minimum current to operate e.g. 5 mA, check the datasheet .The current through R1 is therefore 5mA+100uA, at a voltage across R1 of 6 V, = 1.17 k, so you can choose 1.2 K .
Transistor with Buzzer - Page 1
Forum section: electronics / projects

author: metRo_
author_rank: Regular Contributor
timestamp: September 08, 2013, 08:54:53 pm
content: Hi,I'm trying to drive a buzzer using a BC547 and it is driven by microcontroller. The microcontroller is an Atmega328p.Connecting the buzzer directly to the IO make a loud beep but using the BC547 I almost can't hear it.The buzzer ishttp://www.pololu.com/catalog/product/1260,what do you think is happening?Thanks

author: Andy Watson
author_rank: Super Contributor
timestamp: September 08, 2013, 09:03:34 pm
content: The buzzer appears to a be a piezo (nothing more) which behaves as a capacitor. To make it operate you have to drive current into it and then draw the charge back out, that is you have to sink and source current - a single transistor will only do one.Edit: Ooo! a circuit has appeared! But it doesn't change my previous explanation. When you close the switch the "speaker" will charge up. Then, when you open the switch, .... nothing happens, the piezo remains charged. The datasheet specifies that the speaker is designed to be driven with a 9V p-p square wave, i.e. you have to drive it with a square ware, it's not a buzzer. You could try a resistor across the speaker terminals to remove the charge.

author: metRo_
author_rank: Regular Contributor
timestamp: September 08, 2013, 10:40:03 pm
content: Thanks for your explanationThe resistor make effect but it still doesn't make louder noise than direct driven by the IO pin.How can I do that with two transistors? I think I'll need a H-bridge.

author: Andy Watson
author_rank: Super Contributor
timestamp: September 08, 2013, 11:16:17 pm
content: Do you need the extra transistor(s) ? I'm not an ATmega expert, but I believe it has several outputs which are capable of driving tens of mA (both sink and source). I would connect the piezo direct to the processor - possibly with a 100-200R resistor in series to limit the switching current. If you want to bridge to increase the volume - use two outputs.

author: metRo_
author_rank: Regular Contributor
timestamp: September 08, 2013, 11:27:27 pm
content: after you tell me it is a piezo and it is diferent from normal speakers I searched on internet about it and I to get it louder I need to increase the voltage.

author: Psi
author_rank: Super Contributor
timestamp: September 08, 2013, 11:34:14 pm
content: Try a 470 ohm resistor across the piezo. That will allow current to flow through the transistor.
transition mode boost converter - Page 1
Forum section: electronics / projects

author: johansen
author_rank: Super Contributor
timestamp: August 27, 2013, 08:09:59 am
content: I have invented a method to achieve interleaved phases for transition mode boost converters, while also ensuring it is possible to drop phases if one of them fails, and when that phase drops out the others will automatically compensate.I have a 4 phase prototype below.The two phase prototype works, but it has a glitch during startup when at the start of every 120hz trough, both phases turn on at the same time. So to ensure this doesn't happen the input capacitor has to be big enough that the phases don't drop out, which will limit the PF to about 99% at full load, reduced a bit at low load.The input capacitor also has to be large enough to keep the input voltage ripple (when fed from a current source) below about 25%also, there's another glitch were on the downslope of the 120hz rectifier output, the phases don't spread themselves out properly, they don't overlap, but they do run together, one turning on immediately after the other, you could call that a 90 degree interleaving. (which is actually a known way to reduce the required size of the emi filter.) I think this can be prevented by proper ratios on the current sense resistor.(each boost converter has a current sense resistor, but at the midpoint they are all connected together)specifically: the method by which it forces interleaving is in the current sense resistor. they are all 'on top of' one resistor (actually a bunch of discrete ones in parallel) such that the master current ripple is "on top of" 'all' of the current sense resistors.another method i have thought up is to resistively sum the total current ripple on top of the individual phase currents, doing away with the ultra low impedance board design needed otherwise.photo of the 4 phase versionlarge one herehttp://johansense.com/bulk/boost/4phase_v1.JPGmore info here (the last two posts)http://www.edaboard.com/thread285741.htmlanyhow, i think this is worth patenting, because the method i've used to achieve natural interleaving across any reasonable number of phases also works if an emulated current ramp is used instead of current sense resistors, which is what i'm thinking about building from discrete components.this method of interleaving any arbitrary number of phases would also work for transition mode buck converters.

author: johansen
author_rank: Super Contributor
timestamp: August 29, 2013, 04:57:34 am
content: And the 4 channel version works just as well as 2 phase.i'm really surprised no one is interested.the blue trace btw is dc coupled, it is the voltage running into the current sense comparator.the industry hasn't figured out how to do this without a microprocessor.
Translate thermocouple data capture from Ttype to Jtype??.... - Page 1
Forum section: electronics / projects

author: Smokey
author_rank: Super Contributor
timestamp: August 16, 2016, 04:44:27 am
content: I screwed up my Agilent data logger settings and captured a ton of data with my Jtype thermocouples incorrectly set as Ttype. Any way to fix that without retaking all that data?

author: ace1903
author_rank: Regular Contributor
timestamp: August 16, 2016, 06:56:43 am
content: I would try simple python script for converting to voltage and back to temperature using correct coefficients from:http://srdata.nist.gov/its90/download/type_j.tab
Transmission line FM notch filter in GNUplot - Page 1
Forum section: electronics / projects

author: kronos
author_rank: Contributor
timestamp: October 18, 2021, 05:24:19 pm
content: Hello EEs,I was interested in transmission lines and have been revisiting their theory. They are fascinating.The reason is that I was trying to design an FM notch filter for a wideband HF amplifier, because I get FM stations all over the place when I connect it to a SDR. I wanted to use a transmission line stub as filter, for its simplicity.In order to simulate the effects of such a transmission line and verify the measurements with the nanoVNA, I made a GNUplot script that plots several characteristics of this reference circuit:The scritpt can be found inhttps://github.com/nostromo-1/VNA-plots(file vna_plots.plt), if anybody is interested. It simulates a circuit with a certain output impedance Zs (can be a nanoVNA) connected to a transmission line (characteristic impedance Zo, velocity factor k, length l) and connected to a load Zl.It displays:The Smith Chart as seen by the nanoVNAThe phase of the S11 parameter (reflection coefficient) measured by the nanoVNAThe Bode plot (frequency response) at the output of the nanoVNA (or circuit): modulus of Vi/VsIt can also plot the phase of the frequency response Vi/Vs, and modulus/phase of the frequency response at Zl.As an example, you can connect an RG58 coaxial cable with its end open (open stub) to the nanoVNA (or circuit), and you get the following:It can be seen that the filter works, however it is very very broad: from 50 to 150 MHz. Of course, the Bode plot is not shown in the nanoVNA, but you can see the frequency at which it attenuates most (the length of the coax is \$\lambda \over 4\$ at that frequency) in the phase plot of S11.You can make the notch filter sharper by placing a 50 ohm resistor at the nanoVNA output (that would be the input impedance of an amplifier, where the coax stub is connected at its input):It is now much narrower: from 70 to 128 MHz. However, the transmission line I used as stub was not a coax, but a twisted pair cable (23 cm long) with an 11 pF capacitor at its output (as load, Zl; I actually used an adjustable capacitor). I measured its characteristic impedance to be 104 ohm, and its velocity factor 0.50, with the nanoVNA.Changing those data in the script, it plots the following:It is much shorter than the coax, and it is even narrower due to the higher characteristic impedance: from 83 to 115 MHz.I implemented it, and it works fine. It reduces the interference from the FM stations. However, it is not as sharp, as the input impedance of my amplifer is higher than 50 ohm.
Transmission line parameters - Page 1
Forum section: electronics / projects

author: asheri
author_rank: Newbie
timestamp: March 29, 2016, 11:54:49 am
content: I am trying to characterize a cable by short and open circuit tests to find its parameters the values of R, L, G, and C.R = Z0*alfaL = (Z0*beta)/(2*pi*f)G = alfa/Z0C = beta/(Z0 * 2*pi*f)Could you please advise if these equations (to find the values of R, L, G, and C) are valid for low frequencies, or high frequencies only, or it is only valid for certain conditions, because it does not match the practical measurement (using measurement device called GW INSTEK, LRC-8110G).(http://assets.tequipment.net/assets/1/26/Documents/Instek/lcr-8000g_newproductannouncement.pdf)though I am very sure that they could calculate R and L from impedance of the short circuited, and calculate G and C from the admittance of the open circuit.I watched this youtube videoEEVblog #38 - LCR Meters, Transmission Lines, and Moving goal postsEEVblog #38 - LCR Meters, Transmission Lines, and Moving goal postsDave gives the solution to the first hardware quiz. How do you design an LCR meter? What about a stepped transmi...EEVblog #38 - LCR Meters, Transmission Lines, and Moving goal postsCould you please tell the mathematical equations that have been used to extract the parameters, because I used the equations were written on the white board but unfortunately did not work very far from the measured values.Your kind assistance in this matter will be highly appreciated.

author: danadak
author_rank: Super Contributor
timestamp: March 29, 2016, 02:03:24 pm
content: These types of measurement ?http://web.inf.u-szeged.hu/noise/Online/Sensors/Measuring_Cable_Parameters.pdfhttp://home.sandiego.edu/~ekim/e171f00/lab1.pdfRegards, Dana.

author: Alex Trofimov
author_rank: Contributor
timestamp: March 31, 2016, 11:21:29 am
content: The frequency may matter, because, the more the frequency, the more is influence of reactance over resistance.Cable characteristic impedance is specified at 100MHz typically. But it's related to telecomminication, I'm not into radio and microwave stuff, so it may differ.The formulas you wrote seem very strange to me)Z0 is characteristic impedance. It equals to square root of (L /C). There's no relation to R, which is resistance.May experts in complex numbers stuff correnct me if I'm wrong,("w" is omega)@ short circuit: Z1 = R + j w L@ open circuit: Z2 = R + j w L + 1 / (j w C)Z2 - Z1 = 1 / (j w C)C = - j / (2 Pi f (Z2 - Z1))This way you may measure R with multimeter and get L from Z1 etc.I'm not sure is it what you needed, hope it helps. :-)
transmit collected datalogger data via NFC/RFID - Page 1
Forum section: electronics / projects

author: otaylor
author_rank: Newbie
timestamp: January 12, 2016, 01:53:08 pm
content: Hey guys,I'm trying to build some kind of datalogger where an ATMega measures every 5 minutes the temperature and stores the values into an EEPROM. That's working so far.As the logger should be a portable device powered by a battery, my next step would be to read out the stored data with my smartphone by NFC.However I didn't work out an adequate solution yet. The best case would be if the required energy to transmit the data is provided by the smartphone. I attached a simple sketch how everything should work in my mind: The smartphone sends a command via NFC to my device which sends an interrupt to the microcontroller. The microcontroller sends then the stored data which is transmitted via NFC to the smartphone.But I still didn't figure out which NFC-chip to use. (What about the PN512? ) Would everything work as I imagine it should? Did someone of you realize a similiar project yet or do you have any hints?Thanks a lot and best regards!

author: Fred27
author_rank: Unknown
timestamp: January 12, 2016, 03:31:42 pm
content: ST already have an evaluation board that does pretty much that. I can't remember if it logs temperature, but it certainly has a microcontroller connected to an EEPROM that can be read via NFC.http://www.st.com/web/en/catalog/tools/FM116/SC1444/PF253360?sc=m24lr04e-discovery

author: otaylor
author_rank: Newbie
timestamp: January 14, 2016, 08:27:20 am
content: Alright, thanks that looks quite nice. However the passive device isn't working at all once the NFC-device is removed. And I don't see an option how to add a battery to / modify this board... aren't there any selfbuilt options?

author: Fred27
author_rank: Unknown
timestamp: January 14, 2016, 10:14:34 am
content: Well you said you wanted to use an ATmega anyway. You should be able to design whatever you want and power it however you want, using the M24LR as the interface to your phone.The evaluation board might give you a head start playing with the M24LR and a reference for your design.

author: otaylor
author_rank: Newbie
timestamp: January 19, 2016, 08:55:18 am
content: yeah sure, that's right. I just ordered one to check it out
Help me transmitte 5v,150khz pulse for Long distance wired - Page 1
Forum section: electronics / projects

author: Danesh_SA
author_rank: Contributor
timestamp: September 06, 2017, 07:45:28 pm
content: Hi guys,Recently im working on a project and i want to transmitte two 5v and 150Khz pulses, these pulses have 90 degree phase difference. the distance is about 75m .1-How should i send these pulses and they are reliable?2-is it possible to use RS485 PHY (ADM485) for each of these pulses?3-how is it possible if i dont use uC?Thank you.

author: moffy
author_rank: Super Contributor
timestamp: September 08, 2017, 01:19:07 am
content: According to:https://www.maximintegrated.com/en/app-notes/index.mvp/id/3884,you can transmit up to 1Mb/s over 900 feet of cat5 using RS485. So the simple answer is that it should work easily over the correct cable.
Transparent 802.11-Serial Bridge? - Page 1
Forum section: electronics / projects

author: TheAdmiralty
author_rank: Contributor
timestamp: January 17, 2017, 08:59:03 am
content: Evening, guys!I'd asked something similar in the past, but I'm back with another question. Long story short, I'm working right now on interfacing a small vehicle with a smartphone - we need the ability to send a small number of commands from an application to an access point hosted by the vehicle (think a mars rover).I'm looking into either one of the cheap ESP8266 modules, or something like Microchip's RN1810E. I've been busy with the rest of the power delivery and control system, so I haven't had much time to deal with actually playing around with either of these in hardware, meaning I only know what was explained in the datasheets... and for the ESP-xx, that means absolutely nothing. As it stands right now, I need a device where I can connect a client device to its hosted wireless network, telnet into that IP at a certain port, and send ASCII data transparently over a UART without dealing with the network stack.I've read that these ESP modules can be flashed with something called 'esp-link' which will do this, but I can findnothingon how to reload new firmware onto these reliably. I specifically am dealing with a handful of ESP07 modules. With Microchip's 'WiFly' modules I feel like this is entirely possible, but I can't seem to find any sort of application note with details on how to get it working.Any thoughts? Has anyone else out there needed something like this in the past that would be willing to elaborate?

author: andtfoot
author_rank: Unknown
timestamp: January 17, 2017, 11:48:39 am
content: I have no idea about the modules/chips you are talking about, but as for wifi->serial maybe something like this can be adapted?https://www.globalcache.com/products/itach/wf2slspecs/It's RS-232, but maybe there's a level converter chip that could be bypassed.

author: deebee
author_rank: Newbie
timestamp: January 18, 2017, 03:17:17 am
content: Hi,I have recently required something similar and tried thishttp://www.roboremo.com/esp8266-tcp-to-serial.htmlI looked at esp-link as well but also found this alternative. I used the Arduino IDE version and set it up in station mode but it also has an AP mode if that is preferred. Initial tests showed it to be working well although I have not tried it long term in the real application yet.Might solve your problem. Was very easy to install and use and looks like it could be customised easily.
Transparent knobs? - Page 1
Forum section: electronics / projects

author: komet
author_rank: Unknown
timestamp: July 04, 2013, 10:30:07 pm
content: I got some of these illuminated rotary encoders:http://ch.mouser.com/Search/ProductDetail.aspx?R=PEL12T-4225S-S1024virtualkey65210000virtualkey652-PEL12T4225SS1024They look great, but I couldn't find any transparent knobs to go with them, neither at Mouser nor at Digi-Key. Does anyone know of a source?Thanks for any hints.

author: ddavidebor
author_rank: Super Contributor
timestamp: July 04, 2013, 10:47:32 pm
content: Looooh pornographic

author: trophosphere
author_rank: Frequent Contributor
timestamp: July 04, 2013, 10:51:20 pm
content: Those look like they would be compatible with the knobs thatSparkfunhas.Otherwise, you can try making your own by using some cut solid acrylic tubing.

author: Bored@Work
author_rank: Super Contributor
timestamp: July 04, 2013, 11:07:42 pm
content: https://www.elfa.se/elfa3~tr_en/elfa/init.do?sq=famid101361

author: johnnyfp
author_rank: Frequent Contributor
timestamp: July 04, 2013, 11:30:30 pm
content: I got some of those as well.Haven't quite figured out why I bought them or what I'm going to do with them. But they looked pretty on the website

author: jvdb
author_rank: Contributor
timestamp: July 05, 2013, 12:23:55 am
content: These are clear:450-AA150C - Eagle Plastic Devices - CLEAR 15mm D-SHAFTI used them with this Bourns rotary encoder:PEC11-4215F-S0024
Transplanting 'safety circuit' from a dead LiPoly pack...thoughts? - Page 1
Forum section: electronics / projects

author: bsodmike
author_rank: Regular Contributor
timestamp: July 06, 2020, 07:11:29 pm
content: Hi all,I found a "raw" LiPo that I was able to charge using one of the Sparkfun battery charger circuits.The LiPo that is dead has protective circuitry, so I'm thinking I can transfer this across to the raw pack?Both packs are ~2000mAh, but can't really be sure about the raw pack.Both 3.7vdcthoughts?

author: thm_w
author_rank: Super Contributor
timestamp: July 06, 2020, 08:30:01 pm
content: Should be fine, as packs are similar in size (so protection board specs would likely be appropriate).If possible, have the cell mostly discharged before working on it. Have some fireproof surface to work on, use non-conductive tape to cover up everything, etc.

author: filssavi
author_rank: Frequent Contributor
timestamp: July 06, 2020, 09:03:05 pm
content: The problem I see about it is that you have actually no way of knowing if the safety circuit does indeed work...If I had to guess I would say it is probably dead. There are two ways to kill a battery completely dead (it does not even charge) either it has been overdischarged (which shouldn’t be possible if the safety circuit works, as it is one of the things it is designed. To avoid) or the pass transistors in the protection IC do not stay on. In any case that board is probably shotThe only failure mode that might leave the safety circuit intact is just old age, however I have yet to see a battery that had been used so much that it actually stops charging

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 06, 2020, 10:06:10 pm
content: Quote from: filssavi on July 06, 2020, 09:03:05 pmTest it with a capacitor instead of the battery and do a slow charge/discharge using a resistor and bench power supply. The time constant should be on the order of a few 10s of seconds.

author: bsodmike
author_rank: Regular Contributor
timestamp: July 07, 2020, 06:48:26 am
content: The old pack is very very dead. Nothing to talk about on the output end.