hybridfree/eevblog-posts huggingface dataset:
Different USB Hub mode power connection - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: June 17, 2024, 11:31:32 am
content: I have a question on this USB Hub USB2512B, whose checklist is given here:https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/SupportingCollateral/SchematicChecklistUSB2512BQFNRevA.pdfOn the pages 3,4,5 of the above document, they mention 3 different modes. Self powered, self powered with permanently attached host and bus powered.However, when you look at the VBUS_DET pin of all the 3 different modes, you see that in all the 3 modes, the VBUS_DET pin is only provided with +3.3V input. In that case, how are the 3 modes being differentiated?Can someone clarify on this?

author: SeanB
author_rank: Super Contributor
timestamp: June 17, 2024, 11:45:48 am
content: Page 2 item 4 tells you how it should be connected. The rest is set in the configuration, though to the chip itself there is no difference at all in how it responds in all 3 modes, it still will act as a hub. You also have pin28 telling if local or bus power, if the device is using the internal default configuration.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 17, 2024, 11:52:11 am
content: Logically speaking all are the same. It's a distinction of physical implementation. The chip don't care, it only need 3v3 on the VBUS to indicate connection.Self powered just means the chip got its own independent 3v3 supply. VBUS is derived from USB port's Vcc pin only for indication.Self powered permanently attached is the same as above, but since the other end is permanently attached to the chip (on the same PCB etc.) and both are powered from the same 3v3 supply then you can just attach VBUS to the 3v3 supply. The idea here is that since they both powered from the same supply and both will be active when supply is present then you can use the supply itself as VBUS indication.Bus powered means the chip is powered from USB port Vcc instead of getting its own independent supply. VBUS pin is still doing the same thing as above.

author: Freshman
author_rank: Regular Contributor
timestamp: June 17, 2024, 12:22:55 pm
content: Thank you for the answer.In that case, if all are the same logically, why is there a need to create a difference?Like, regardless of the 3 modes, just plug 3.3V to VBUS and it should be fine right?Any idea or reason/example where these distinctions will be helpful in an application?

author: ejeffrey
author_rank: Super Contributor
timestamp: June 17, 2024, 05:17:05 pm
content: For self powered hubs when not permanently attached the VDET_bus comes from the USB host, not the main power supply. For the other two options there is only one power supply so there is no distinction that's all it's trying to show here.In addition, there is a separate pin to tell the hub if it is bus powered so that it advertises as such and the host will prevent high power devices from being activated.
Different values on SMD capacitor - Page 1
Forum section: electronics / beginners

author: peter_s
author_rank: Newbie
timestamp: December 11, 2020, 02:33:48 pm
content: can someone help with this issueI'm trying to replace three components on a board, 2 capacitors and 1 resistor,I am using a BSIDE tester to identify and test, I don't have much faith in this device for accurate readingsI removed the same components from an identical board,the capacitors are of 0805 type with no markings, beige in colour,when i measure the value i get 220nf esr 3.5oHms , if i turn the smd around and measure again i get 37pf with no esr reading. which reading is correct, and what value capacitor do i replace it with.the resistor gives me different readings also unmarked and grey in colour, i get a reading between 0.38 on BSIDE and 0.5 oHms on a regular multi-tester, again do i replace with a 0.5 resistor. .Thanks

author: Digorion
author_rank: Contributor
timestamp: December 11, 2020, 06:49:24 pm
content: How did you determine that it is a resistor / capacitor? The top arrow indicates inductance (according to the markings on the PCB), the second (bottom) indicates the capacitor. Are you sure you have correctly identified the component type? Perhaps this led to the incorrect definition of values.
Differential ADC input range - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: January 02, 2018, 10:54:09 pm
content: If I have a differential ADC such as this one:http://www.ti.com/lit/ds/symlink/ads1115.pdfCan I supply voltages higher than VDD/VCC on the two pins as long as the differential is less than VDD+0.3V?EG:Vcc: 5VAIN0: 8.4VAIN1: 11.1VAnd configure AIN0/AIN1 as a differential pair. Will it read for 3.7V or will it let the smoke out?

author: retrolefty
author_rank: Super Contributor
timestamp: January 02, 2018, 11:07:30 pm
content: Analog pins must not be beyond GND – 0.3 VDD + 0.3. While the input can be configured for differential between two input pins this does not me they are bipolarity inputs, negative voltages are not allowed.This is more a digital signed mode Vs a digital integer mode. It's subtle and often missed.Quote

author: paulca
author_rank: Super Contributor
timestamp: January 02, 2018, 11:23:59 pm
content: Aww well, it means external diff amps then. No big deal, thought I had found a short cut.

author: danadak
author_rank: Super Contributor
timestamp: January 02, 2018, 11:41:36 pm
content: You can tie an R to Vcc to input and one from that input to signal,a third to ground, and offset the voltage seen by A/D. That will allowhandling a negative signal. Attached a calculator to help selectingthem. Be careful of input Z structure of A/D when you choose values.This is one simple method. It has errors due to non precision of Vcc(use a reference) and R tolerance (use precision Rs).Regards, Dana.
SORTED - Differential Amp - BJT working, JFET not working - Page 1
Forum section: electronics / beginners

author: tron9000
author_rank: Frequent Contributor
timestamp: November 03, 2015, 09:50:01 am
content: So I have 2 Identical differential amp circuits:R1 & R2 =10k, & R3 & R4 = 100k, giving a gain of 10.http://www.electronics-tutorials.ws/opamp/opamp_5.htmlI have the inputs to the inputs to the amp across a 1R resistor with another 1R resistor in series with a variable power supply across both. adjust the voltage and the current increase in the circuit and the voltage out of the amplifier will be 10x the voltage across the resistor (V=IxR)I'm running off a single rail, 12V supply for the diff amp cct.If I use a BJT input op-amp: the LM324 - it works well;Vout = 10x (IxR)If I use a JFET input op-amp: the TL074 - I get some weird results:Vin/VVout/VGain0.111.3271070.211.32856.640.311.25337.510.44.75511.8870.54.0058.010.63.8856.4750.73.6595.2270.84.1505.1870.96.1606.8441.08.1688.168where Vin is measure across the 1R resistor on input to amp, so the voltage goes from 0.2V to 2V, I've looked at the data sheets for both and the common mode ranges seem to confirm that they should work within that voltage.Are JFET input op-amps just not designed for this roll? Or have I overlooked something?

author: Andy Watson
author_rank: Super Contributor
timestamp: November 03, 2015, 10:06:39 am
content: The common-mode voltage input range of the TL074 is not rail-to-rail. The datasheet suggests that it operates -12 to 15V with +/- 15V supplies, i.e. 3V above the most negative supply rail (0V in your case).

author: tron9000
author_rank: Frequent Contributor
timestamp: November 03, 2015, 10:15:13 am
content: So I've overlooked something - right I think I understand now where I've gone wrong: cos (as you stated) the common voltage range for a +/-15V goes -12v to +15v, and that cos I'm using a single supply rail that output is effectively 3 to 12V?

author: tron9000
author_rank: Frequent Contributor
timestamp: November 03, 2015, 01:21:44 pm
content: yep, just stuck the TL074 on +/-12V supply rail and managed to get some sensible linear readings from 0 to 1A current. Fell into a trap!
Differential amp circuit outputting positive voltage regardless of polarity - Page 1
Forum section: electronics / beginners

author: king.oslo
author_rank: Frequent Contributor
timestamp: July 27, 2012, 08:45:23 pm
content: Hello there,An op-amp voltage subtractor outputs a negative voltage if the inverting input voltage is greater than the non-inverting input voltage.I want to make a circuit which always always subtracts the lowest voltage from the highest voltage. I want to always get a positive output. How can I do that elegantly? It doesn't need to use an op-amp, but its got to have less than 1mV input offset and high speed.What do you suggest?Thank you for your time.Kind regards,Marius

author: chrome
author_rank: Regular Contributor
timestamp: July 27, 2012, 09:38:42 pm
content: Differential opamp followed by an opamp rectifier ?

author: erupter
author_rank: Contributor
timestamp: July 28, 2012, 03:04:56 pm
content: Checkthis linkby Elliot Sound Products for precision rectifiers.
differential amplifier - Page 1
Forum section: electronics / beginners

author: backd00r
author_rank: Contributor
timestamp: February 29, 2016, 05:01:09 pm
content: I would like to know what are the advantages and disadvantages of using an opamp differential amplifier in a circuit?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: February 29, 2016, 05:33:18 pm
content: They are small.(In other words, you have not provided enough information for someone to give a reasonable answer. What kind of circuit are you considering, what kind of differential op-amp, etc.)

author: Aodhan145
author_rank: Frequent Contributor
timestamp: February 29, 2016, 10:28:02 pm
content: What do you mean that is a typical building block circuit. There are no disadvantages or advantages. There is just knowing when to use it . If you had a particular situation there may be advantages or disadvantages.
Differential Amplifier did'nt work - Page 1
Forum section: electronics / beginners

author: Eldi4
author_rank: Contributor
timestamp: June 30, 2019, 03:15:50 pm
content: Hi,I have some differential amplifier for hi-side current sensing that did'nt work, the output is always sitting on 3.8V whatever the condition is (no current/current flow), the one that did'nt work is the bat and load side (same symptoms), the diagram is on the attachment, i used 10k/220k for 22 gain for both amp (bat and load) instead of what is showed on the diagram, the amp is powered with 5V single supply, i have tried to replace the IC with other LM358, but the problem remains the same.However, i had differential amplifier with 47 gain (1k/47k) that did work, it powered with 5V too, the diagram is attached too.What probably is the problem?NOTE : The bat diff amp and load diff amp is on different IC, not like what is showed on diagram.

author: capt bullshot
author_rank: Super Contributor
timestamp: June 30, 2019, 03:27:08 pm
content: Quote from: Eldi4 on June 30, 2019, 03:15:50 pmYour circuit places an input voltage at the LM358 that is way above its supply voltage.You must observe the allowed input voltage range (differential and common mode) of the amplifier, having a 5V supply doesn't cover 12V common mode voltage.

author: Eldi4
author_rank: Contributor
timestamp: June 30, 2019, 03:32:03 pm
content: Quote from: capt bullshot on June 30, 2019, 03:27:08 pmSo, using 12V supply should fix this problem then?My PV voltage is even 30V, but the current sensing was seem to be working when the voltage was dragged down to 0.7V because of diode short circuit, but no idea when the voltage is 10V+ (havent tried it yet).How can i solve problem for those diff amps?

author: capt bullshot
author_rank: Super Contributor
timestamp: June 30, 2019, 03:48:43 pm
content: Quote from: Eldi4 on June 30, 2019, 03:32:03 pmNo, not in general. Observe the specifications of the amplifier and do the calculation of your circuits common mode voltage. Most simple and cheap amplifiers require some headroom between the supply voltage and the input voltages. Look for an rail-to-rail input if you want to supply the amplifier from a voltage that is equal or greater than your max. common mode voltage.QuoteThe circuit is the same, so it will behave the same.Quote- There are special "current sense" amplifiers that are designed to work under such conditions - ready to buy from the major suppliers (TI, ADI).- You can build your own current sense amplifier using some tricks, you might be able to find such circuits e.g. in the datasheet of the OPA333.- Add noise gain to your circuit (this will increase common mode voltage for the cost of reduced accuracy and increased noise).- If applicable, use low side sensing

author: Eldi4
author_rank: Contributor
timestamp: June 30, 2019, 03:58:18 pm
content: Thanks for the explanation!I will go for low-side sensing, the quick and costless way...
Differential Amplifier - Differential Mode - Page 1
Forum section: electronics / beginners

author: EEM
author_rank: Newbie
timestamp: June 26, 2016, 05:07:56 am
content: Hello, I am hoping someone could help me with part B of this problem. I am not sure of the effects the resistor would have on the differential output gain.Also I have attached my solution to part A but I am uncertain if I derived it correctly.Any help would be appreciated !

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 26, 2016, 05:26:39 am
content: b. A resistor between outputs acts in parallel with (Rc + Rc), so reduces gain by that amount. No effect on CM.Tim

author: EEM
author_rank: Newbie
timestamp: June 26, 2016, 07:29:28 pm
content: Thanks Tim !I've attached my proof for b. Does this look OK ?Also, I thought the added resistor would affect Vo1, so why would there be no effect on CM gain ?

author: Marco
author_rank: Super Contributor
timestamp: June 26, 2016, 07:38:10 pm
content: Quote from: T3sl4co1l on June 26, 2016, 05:26:39 amWith common mode gain they mean the gain for a single ended output (not the differential gain with transistor mismatch as is common). Because of Ree this will change.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 26, 2016, 07:39:15 pm
content: Hmm, it should be 3, not 4.What is the definition of differential output voltage? Common mode?Tim

author: TimFox
author_rank: Super Contributor
timestamp: June 26, 2016, 07:49:03 pm
content: delta[Vout(diff)] = delta [Vout(1) - Vout(2)]delta[Vout(cm)] = (1/2) x delta[(Vout1 + Vout2)]

author: LvW
author_rank: Frequent Contributor
timestamp: June 27, 2016, 09:12:52 am
content: Quote from: EEM on June 26, 2016, 07:29:28 pmNo - it doesn`t.You have forgotten that the third (new) resistor is not at signal ground at one leg.
Differential amplifier IC - Page 1
Forum section: electronics / beginners

author: mitrynicolae
author_rank: Contributor
timestamp: April 30, 2019, 09:08:19 am
content: Hello everyone,Does anybody know any IC that matches all the following requirements:- it is a differential amplifier- it has a 0.1 gain- can operate on a single 5V power supply- AND is rail to railFor example AD628A meet all the above conditions, except is not rail to rail.Thanks!

author: pwlps
author_rank: Frequent Contributor
timestamp: April 30, 2019, 09:17:12 am
content: You can assemble your own 0.1 gain differential amplifier using an opamp and resistances.The low voltage family TLV277x (x=0,1 etc) is said to be rail-to rail output.
Differential amplifier MOSFETs - Page 1
Forum section: electronics / beginners

author: kingkings
author_rank: Newbie
timestamp: June 13, 2020, 06:21:19 am
content: can someone help me solving those questions it doesnt have to be all points but any point ( a , b ,c ..etc) you can do and i will be grateful

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: June 13, 2020, 08:37:52 am
content: What specifically do you need help with? What can/can't you do? I would help but I'm not just gonna solve a random exam/test question online.

author: Wimberleytech
author_rank: Super Contributor
timestamp: June 13, 2020, 04:34:49 pm
content: ^^^^^^^^^^^^^^ DittoYou take shot and solving it yourself...show us your work and we will assist.

author: kingkings
author_rank: Newbie
timestamp: June 13, 2020, 05:10:01 pm
content: i solved similar question with different bias current but i guess its a bit crappy

author: Wimberleytech
author_rank: Super Contributor
timestamp: June 13, 2020, 05:41:09 pm
content: Yeah, pretty messy. So this is the solution for a different problem?Your expression for gm is incorrect.gm = (2K*I*W/L)^1/2Here is a little hint. Calculate currents in M2. You are given the currents in M1 (via tail). Apply KCL at the drains of M1.
Differential Amplifier Shoots to vc - Page 1
Forum section: electronics / beginners

author: Jamadir
author_rank: Newbie
timestamp: June 07, 2020, 04:13:17 pm
content: Hello, i build a pcb with an LM 358 Opamp in a differential setup. It's used to measure the voltage Difference over a shunt in the range of 0 to 0.1v (around 12v).It's supplied with 5v and ground. But somehow it just shoots up to 5.5v What did i do wrong? The Gain should be 47.Thank you for your help!

author: Andy Watson
author_rank: Super Contributor
timestamp: June 07, 2020, 05:11:24 pm
content: Quote from: Jamadir on June 07, 2020, 04:13:17 pm?Are you saying that you have a 12V of common-mode voltage - and a supply voltage of only 5V ?Assume that the circuit works. Calculate the voltages you would expect to see at the inputs to the op-amp. Then have a look at the data sheet - specifically the common-mode input range.

author: Jamadir
author_rank: Newbie
timestamp: June 07, 2020, 05:15:32 pm
content: It's a DC circuit, what do you mean by common mode voltage? I thought a Differential amplifier would only care about the difference (say 12v and 12.1v).

author: Andy Watson
author_rank: Super Contributor
timestamp: June 08, 2020, 01:16:08 am
content: The common mode voltage will be \$\frac{12 + 12.1}{2}\$ - i.e. the average of the input voltage.
Differential amplifier voltage controlled gain miscalculation - Page 1
Forum section: electronics / beginners

author: setq
author_rank: Frequent Contributor
timestamp: August 05, 2016, 10:45:02 pm
content: First post, so hello and I'll make this a good oneI'm working through a relatively ancient 1st edition copy of The Art of Electronics and the old Lab manual, not homework. Too old for homework now. I've just completed the section on transistors and am doing the additional exercises at the end and am stuck on their differential amplifier voltage gain determination.The question (6) describes the following:In this problem you will ultimately design an amplifier whose gain is controlled by an externally applied voltage. (a) Begin by designing a long tail pair differential amplifier with emitter current source and no emitter resistors (undergenerated). Use +/-15 volt supplies. Set Ic for each transistor at 1mA and use Rc=1k. Calculate the voltage gain from a single ended input (other input grounded) to a single-ended output.Did that and it works in LTspice and on paper.Now modify the circuit so that an externally applied voltage controls the emitter current source. Give an approximate formula for the gain as a function of controlling voltage.This is described in the following LTspice screencap. As Gm is related to total current of the long tailed pair I thought we can just adjust the current source:I used the following calculations:Re = .025 / Ic -> This is the emitter resistance at the collector current specified by Ebers Moll.Ic = (Vc - 0.6) / R1 -> This is the collector current controlled by the current sourceGm = R2 / 2rE -> This is the gain ignoring any emitter degeneration resistors as there aren't any.Substituting these in for the above gives me:Gm = (0.00125 * R2 * R1 ) / (Vc - 0.6)When I throw this in LTspice with a voltage of 1.6v and resistors of 1k, 500 ohms as calculated I'm getting a gain of 625If I put a 10mV p-p sine into the simulation however, I'm getting a p-p of 350mV which is a gain of 35.Can anyone see where I've gone wrong here - I'm completely stumped? Any help appreciated!

author: PChi
author_rank: Frequent Contributor
timestamp: August 06, 2016, 01:53:21 pm
content: Isn't Gm = R2 x (Vc - 0.6) / ( 2 x 0.025 x R1 ) ?I make that 40 and LTSpice is adding in the effect of the finite collector resistance of Q4 dropping the voltage gain to 35.

author: setq
author_rank: Frequent Contributor
timestamp: August 06, 2016, 03:42:36 pm
content: Interesting and much closer! How did you derive that from the schematic?

author: PChi
author_rank: Frequent Contributor
timestamp: August 06, 2016, 05:18:32 pm
content: I just rearranged the equations that you listed.Gm = R2 / 2ReRe = .025 / Ic so 1 / Re = Ic / 0.025Substituting for Re in the equation for Gm = R2 x Ic / (2 x 0.025)Ic = (Vc - 0.6) / R1Substituting for Ic in the equation for Gm = R2 x (Vc - 0.6) / ( 2 x 0.025 x R1 ).

author: setq
author_rank: Frequent Contributor
timestamp: August 06, 2016, 07:02:24 pm
content: Gotcha that makes sense now. I fudged my algebra completely.Thanks for your help - much appreciated!
differential amplifier with active load - Page 1
Forum section: electronics / beginners

author: fady232
author_rank: Contributor
timestamp: May 19, 2025, 01:48:13 pm
content: Differential amplifier with active loadHello, im simulating this circuit that is similar to the differential amplifier, but this time the collector current is given by a current mirror circuit.But there are multiple things that i dont understand, like how u calculate the gain of this circuit? and how i set a precise gain?The collector current depends on the costant current generator at the bottom? like if i set a costant current generator of 4mA, then i will have that current mirror will generate 2mA on both ic lines?

author: MariuszD
author_rank: Regular Contributor
timestamp: May 19, 2025, 02:58:08 pm
content: Quote from: fady232 on May 19, 2025, 01:48:13 pmThis circuit is used to make maximum possible gain. Gain in not stable. Gain is not important. It is useful in comparators and circuits with global feedback loop (op amps).Quote from: fady232 on May 19, 2025, 01:48:13 pmThere is no load. In balance you have 2mA on both lines. Slight imbalance leads to saturation.When there is a load connected to collector of Q3 currents can be different. Q1 and Q2 is a current mirror. So currents from Q3 and inverted current from Q4 are added at the load.

author: TimFox
author_rank: Super Contributor
timestamp: May 19, 2025, 04:26:45 pm
content: As drawn, this circuit is a voltage-in, current-out (transconductance) amplifier with a quite high output impedance (not well-determined impedance) and an ill-defined output voltage.Normally, such a circuit is followed by a low-impedance load to a well-defined voltage, such as the base of a common-emitter BJT stage, which, in turn, can be analyzed as a current amplifier into its load resistance.In op amps, this BJT stage often has a feedback capacitor from collector to base to determine the AC gain.
Differential to single-ended and vice-versa - Page 1
Forum section: electronics / beginners

author: Ozracing
author_rank: Contributor
timestamp: September 23, 2017, 08:06:03 pm
content: Hello,I have this idea of making an audio amplifier with couple of TPA3255 and a bluetooth module, but i can't find any info on how differential signaling (balanced?) could be connected from the bluetooth module to the amplifier inputs.As far as i know the pair of positive and negative needs to run close together from point A to point B and they should be equal length, but i can't find any info how i could simultaneously run a pair from point A to point B1, B2, B3. Do i need fully differential op-amps or what's the deal with that? Any pointers on what to look for?I have attached an image of how i want to connect them.UPDATE: thinking of using some op-amps to convert the signal from differential to single-ended then using some active low-pass & high-pass filtering and then converting back to differential from single-ended just before the TPA3255 amps where needed. Would this be electronically good?
Differential Gomes Amplifier using pentodes in ultra linear mode? - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: January 25, 2020, 02:26:39 pm
content: I found this:[ Attachment Invalid Or Does Not Exist ]and wanted to modify it so it uses pentodes as the power tubes, and have a transformer with taps for the screen grids so I can switch the pentodes from "pentode" to "triode" mode and have the pentode mode be ultra-linear.but where would I connect the screens for the top pentodes?is this even possible?also, I intend to put 2 chokes in series with the plates of the top pentodes to it's a parafeed style output stagethat's possible right? I don't really see a reason why that wouldn't be but correct me if I'm wrong.

author: Circlotron
author_rank: Super Contributor
timestamp: January 25, 2020, 10:19:29 pm
content: I would run the screens of the upper pentodes to +600V through a resistor, and to the ultra linear tapping through a large capacitor, similar in principle to how the anodes of the upper outer triodes are fed.I don’t think the two chokes at the top are going to do anything useful. More likely just cause problems. Parafeed is unnecessary in this topology.

author: gbaddeley
author_rank: Regular Contributor
timestamp: January 27, 2020, 01:19:21 pm
content: 12B4 is a low Ra and low mu triode. You would need to think very carefully about using pentodes / tetrodes in such a circuit, as they have much higher Ra and mu.
Differential input in a mux?  - Page 1
Forum section: electronics / beginners

author: erikbrenn
author_rank: Regular Contributor
timestamp: August 13, 2019, 08:44:41 pm
content: Hi,I understand a differential input in terms of an amplifier.But what's the purpose of an differential input in e.g the AD659 multiplexer? Does a channel switch out the difference voltage between the two inputs?For what? Signal-noise ratio stuff??cheers,Erik

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: August 13, 2019, 09:08:20 pm
content: There is nothing special there, its a convenient matrix to put infrontof a differential amplifier.Study the logic diagram in the datasheet.The convenience is that a0 and a1 control eight switches. You don't need eight logic lines because only certain patterns make sense in this scenario.

author: erikbrenn
author_rank: Regular Contributor
timestamp: August 13, 2019, 10:17:02 pm
content: QuoteI'm afraid that didn't help....QuoteI did. There is nothing to it as you say.QuoteWell not really, two address lines can only control four switches, logically speaking. That was the reason for my confusionI'll rephrase :Will it ever make sens to provide different analog inputs on one channel with two differential inputs?If yes, what for?If no, why does this setup exist, why not just use a single ended analog mux like AD658? (which has 8 channels, but still same pin-count)cheers

author: ledtester
author_rank: Super Contributor
timestamp: August 13, 2019, 11:01:56 pm
content: Here's an example application... Suppose you have 4 stereo audio inputs. With a single ADG659 you can select one of those inputs (a left and right channel pair) for processing, output to an amplifier, etc. If you used a AD658 you would need two of those chips - one for each channel (left and right).

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: August 14, 2019, 12:41:38 am
content: Quote from: erikbrenn on August 13, 2019, 10:17:02 pmSo its very hard to talk to someone who seems to be overcomplicating things. Obviously one control line, being an output, can be an input to any number of switches. Any number. So, the reason, here, is because inputs to a differential amplifier or an instrumentation amplifier come in pairs, V+ and V-. It is *not* generally useful to have any V+ paired with any V-. So they want to be in synchrony. That is what that switch does for you. Maybe it is so simple you are having a hard time with it!When you do need more flexibility you simply *do* use separate multiplexers and then you need a microcontroller or something to make it work.Consider the audio analogy and realize that you do not want to have a common ground. You will see that whenever one input is switched in that requires exactly something like the ADG659. (Hint: does it make sense to have an audio input where V+ comes from your cartridge and V- comes from your mp3 player?)Hope this helps.
Differential Oscilloscope Probe Schematics? 💕  - Page 1
Forum section: electronics / beginners

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: December 20, 2023, 06:56:24 pm
content: Hello all, I've been trying to find schematics for essentially *any* differential oscilloscope probe schematic (above 50MHz, preferably 100MHz or greater) from a reputable OEM (Sapphire, Lecroy, MicSig, Rigol, etc.) so thatI can get the PCB manufactured to DIY the probe myself. I'm not interested in purchasing one of the low-cost ($100-$200) differential probes with only a 10-50MHz bandwidth from Hantek/similar.I understand that it won't be as "safe" (I won't be using it above 100V) and that it won't be entirely linear across the frequency range, however I think it would be a fun project. Myproblemis that I'm having difficulty actually finding any of these schematics. Can anyone help with that?Thanks 💕

author: JacobPilsen
author_rank: Regular Contributor
timestamp: December 25, 2023, 06:34:10 pm
content: Just use a search on this forum (entire forum) for 'differential probe schematic':https://www.eevblog.com/forum/projects/my-first-project-low-cost-differential-probe/https://www.eevblog.com/forum/projects/oshw-diy-1kv-100mhz-differential-probe-(dilemma-vs-hope)/https://www.eevblog.com/forum/testgear/repair-tektronix-p5210-high-voltage-differential-probe/

author: boB
author_rank: Frequent Contributor
timestamp: December 25, 2023, 07:22:51 pm
content: We have several of the Micsig 100MHz probes and a few of them have developed a DC offset. Still usable but not right.David Jones did a teardown and partial schematic of that but of course, the ones I have are slightly different.Was trying to add a cancelling DC offset but the schematic and PCB was different enough that I couldn't quite understand what they had done.Always interested in this kind of stuff.Happy Christmas !boB
Differential output impedance matching - Page 1
Forum section: electronics / beginners

author: veeti
author_rank: Contributor
timestamp: July 26, 2020, 12:46:10 pm
content: HelloI Found really cool project of 6GHz radarhttps://hforsten.com/third-version-of-homemade-6-ghz-fmcw-radar.htmlBut i really can't uderstand his IF output solution from the mixer.-Bias is done via 50ohm resistor, but chip output is 200ohm - doesn't it restrict it?-If Mixer output impedance seems to be 200 Ohm and ADA4940-02 is set to have 1100 Ohm impedance-I allso have tried to find filter calculator to verify/understand the filter design, but the only document which i have found is thishttps://www.analog.com/en/technical-articles/understanding-and-designing-differential-filters-for-communications-systems.htmlAnd from there i can't understand terms"normalized"C1 = 1.433, L2 = 1.594, C3 = 1.433

author: David Hess
author_rank: Super Contributor
timestamp: July 27, 2020, 01:59:35 am
content: The datasheet you linked explains exactly what is happening. The outputs are open collector (1) which means high impedance current outputs. The output impedance is essentially set by the load resistance. In a less critical application, simple 50 ohms pull-ups will yield a 100 ohm differential impedance which will work fine.(1) They could be the collector of a cascode transistor for maximum performance. If not, an external common base cascode stage could extract better performance.
Differential pressure sensors and measures of accuracy - Page 1
Forum section: electronics / beginners

author: KrisKringle
author_rank: Newbie
timestamp: August 22, 2019, 05:08:48 pm
content: Hello, first time poster here!I'm looking at differential pressure sensors for low pressure applications and I'm confused by how the manufacturers describe their sensors' accuracy. I see it is common to describe accuracy as a percentage of the full scale span, %FSS, for example in Table 5, page 4 of Honeywell's RSC series' datasheet (https://sensing.honeywell.com/honeywell-sensing-trustability-rsc-series-data-sheet-32321348-c-en.pdf). How do I relate %FSS to an error in Pascals?Is it correct to relate it to 1% of the ADC's output span? So if the sensor uses a 12 bit ADC, the error is equivalent to 1% of the 2^12 values?Thank you in advance.

author: RoGeorge
author_rank: Super Contributor
timestamp: August 22, 2019, 05:25:41 pm
content: My understanding is like this:If the sensor range is from, let's say 20mbar to 50mbar, then the FSS (Full Scale Span) is 50mbar - 20mbar = 30mbar. 0.1% of 30mbar will be 0.03mbar.If the sensors reads, let's say 25mbar, then the real pressure is guaranteed to be somewhere in the range 24.97..25.03mbar.

author: KrisKringle
author_rank: Newbie
timestamp: August 22, 2019, 05:37:21 pm
content: Thank you, I see. What confuses me now is the attached figure below. It's fromhttps://sensing.honeywell.com/pressure-sensor-glossary-of-terms-tn-008200-2-en-final-08jul11.pdf. It seems to be related to the sensor output there?EDIT:As they say in the same document:Quote

author: RoGeorge
author_rank: Super Contributor
timestamp: August 22, 2019, 06:03:20 pm
content: I'm not sure what exactly is the question related to that chart.Looking at the terminology pdf, in fig.2 are shown all types of errors. According to note 6 in the datasheetQuotethe max 0.01% FSS BFSL includes only the sources of errors drawn in yellow. The 0.01% does not includes other error sources caused by e.g. offset errors or thermal errors.

author: KrisKringle
author_rank: Newbie
timestamp: August 22, 2019, 06:20:33 pm
content: My confusion regarding the chart in fig.1 is due to the offset at the minimum pressure. How do I determine what 0.1 % of FSS is, if I only know the operating pressure range? I see from the datasheet (section 5.0 page 28) that the sensor offers zero correction based on internally stored calibration data. Should I simply assume the minimum pressure offset is zero?If I understand you correctly, a +/- 1 kPa pressure sensor with +/- 0.1% FSS accuracy corresponds to an accuracy of 2000 * 0.001 = 2 Pa? I.e a measured value of 500 Pa is in the range of 498-502 Pa?Thank you.

author: RoGeorge
author_rank: Super Contributor
timestamp: August 22, 2019, 06:38:31 pm
content: Quote from: KrisKringle on August 22, 2019, 06:20:33 pmYes, 498-502 Pa assuming offset error, thermal error and any other type of errors are zero.The best thing to do is ask a support engineer from Honeywell, I never worked with those sensors.

author: KrisKringle
author_rank: Newbie
timestamp: August 22, 2019, 07:07:31 pm
content: Thank you!
Differential probe for HANTEK oscilloscope - Page 1
Forum section: electronics / beginners

author: Bondguy
author_rank: Contributor
timestamp: November 15, 2016, 09:45:19 am
content: Hey guys,Can anyone recommend a differential probe for Hantek scope ( DSO5202B ) - I am not sure if a diff. probe can be used with different scopes or a probe can be used ONLY with a particular scope. Does anyone know?

author: BravoV
author_rank: Super Contributor
timestamp: November 15, 2016, 09:51:42 am
content: Budget ?

author: tggzzz
author_rank: Super Contributor
timestamp: November 15, 2016, 10:16:48 am
content: It rather depends on the signals you want to examine. State thecontextof yourproblem, not just your presupposedsolution.There is just a little bit of difference between looking at a 500V AC signal where neither side is earth referenced, vs looking at a 1V LVDS signal between two ICs.

author: tautech
author_rank: Super Contributor
timestamp: November 15, 2016, 11:23:44 am
content: Pintek DP-25 is about the cheapest new option, can be used on any 1MBNC input scope.
Differential Probe Output Cable Impedance - Does it matter? - Page 1
Forum section: electronics / beginners

author: nidlaX
author_rank: Frequent Contributor
timestamp: June 27, 2017, 07:12:17 am
content: Out of curiosity, does it matter what type of BNC cable is used for the output cable of a (<200 MHz) differential probe? Most manufacturers don't even specify whether they use 50 Ohm or 75 Ohm cable, but I'm guessing 50 Ohm is the standard.

author: tautech
author_rank: Super Contributor
timestamp: June 27, 2017, 08:01:41 am
content: Probably won't matter for LF stuff but they will be 50that matches channel input impedance when 50input is selected.

author: capt bullshot
author_rank: Super Contributor
timestamp: June 27, 2017, 08:09:56 am
content: I wouldn't consider 200MHz LF stuff ...And I'd expect the cable to have 50 Ohms.

author: tautech
author_rank: Super Contributor
timestamp: June 27, 2017, 08:15:13 am
content: Quote from: capt bullshot on June 27, 2017, 08:09:56 amNeither do I. Maybe I should've stated a few 10's of KHz.Quote
Differential probes for noob (est. in US $) - Page 1
Forum section: electronics / beginners

author: bc888
author_rank: Regular Contributor
timestamp: December 06, 2018, 06:11:33 pm
content: New to the game and still learning. The memory of touching mains with a 10' aluminum extension pole while power (pressure) washing a 2 story house eaves has not faded. I was trying to avoid the obvious frayed area where the electrical wire came from the street and entered the home, I "thought" I had plenty of room for safety but the water had other ideas. It bounced over there anyway although I'll admit I don't recall seeing it happen, in fact the memory's get fuzzy in here. I jerked when the power hit and there I stood with my jaws and hands both locked tightly shut, unable to release the extension pole or even open my mouth to involuntarily scream. When I finally dropped, the pole stayed stuck up there. The rubber hose was wet, and I first heard the buzzing, and then saw, that there was a significant blue spark happening @25' away where the hose went over the chain link fence. It stayed there till I was able to stagger off and grab a broom to knock this pole from hell off of contact with the wire. My muscles were sore for weeks.I've got a couple more stories of similar issues with electricity which I care not to repeat. I saw Daves cautionary video on the potential to blow yourself and your oscilloscope up. Shit. I have not touched My brand new scope which was on the way when I saw Dave's vid (thanks Dave!). I have an isolation transformer on the way, and am getting some differential probes. I'm nervous and I'd love to only scope battery powered devices, but suspect I'd trip over my dork in a short period of time and want to prep for the event in advance. I expect I'll have huge gaps in my knowledge, any ideas or thoughts in addition to a vote on a probe that will work for me is appreciated.
Differential signal question - Page 1
Forum section: electronics / beginners

author: jeremy0203
author_rank: Contributor
timestamp: May 14, 2022, 06:46:37 am
content: Hello, I have some LEDs that operate off a 5v signal. The controller outputting the signal is 3v3. I want to pass these signals over a differential driver/receiver such as the TI AM26C31(32). Question is on the way the differential signaling works. Will the signal still be 3v3 on the output of the receiver or will it be buffered to 5v since that is what the voltage input of those chips are? Trying to determine if a buffer on the output will be required or not

author: Zero999
author_rank: Super Contributor
timestamp: May 14, 2022, 09:52:03 am
content: The AM26C31 runs off 5V and has a CMOS output, so will have an output voltage of near 5V, but it will drop when loaded. The data sheet specifies an output voltage of at least 3.8V, when the output current is 6mA.

author: Terry Bites
author_rank: Super Contributor
timestamp: May 14, 2022, 02:03:53 pm
content: It allows for longer faster lines, is less succeptable to interference and emits less interference.The main benefis arrise from the fact that the signal on the pair is not referenced to ground.

author: eugene
author_rank: Frequent Contributor
timestamp: May 14, 2022, 02:29:19 pm
content: Looking at the datasheets (which you should learn to do yourself), the receiver (AM26C32 with 5V supply) has a recommended minimum high level signal input of 2V, which should be achieved by the 3.3V system at the sending end. It has a guaranteed minimum output voltage of 3.8V, which should satisfy the 5V system it's feeding.A bigger problem is that the driver (AM26C31) has a recommended supply voltage of 5V (4.5V to 5.5V.) It might operate on a 3.3V supply, but I wouldn't count on it being reliable.In any case, the voltage mismatch seems counter to the purpose of differential pairs. Finding 5V at the controller end to power the differential driver might be a better solution. Is the controller USB powered? If so, there's 5V available from there. If the controller is some kind of Arduino-like device, then there is likely a pin that will supply 5V.

author: TimFox
author_rank: Super Contributor
timestamp: May 14, 2022, 02:32:43 pm
content: Since RS422 drivers are current limited, they can be used to drive an LED directly across the differential outpout (read the datasheets for details), but be careful about the reverse voltage limit on the LED.Where did the LEDs in your original question fit into the circuit?

author: jeremy0203
author_rank: Contributor
timestamp: May 15, 2022, 12:46:46 am
content: Both ends are powered via 5v. Basically just curious if even though the signal input is 3v3 if the device basically buffers it up to it's supply voltage. So is the differential output 5v after the fact or does it get retained at 3v3

author: eugene
author_rank: Frequent Contributor
timestamp: May 15, 2022, 01:57:10 pm
content: Quote from: jeremy0203 on May 15, 2022, 12:46:46 amSignal output levels depend on the supply, not the signal inputs.
Differentiator output - Page 1
Forum section: electronics / beginners

author: renzoms
author_rank: Regular Contributor
timestamp: October 23, 2019, 10:02:47 pm
content: So I’ve wrapped my head around Differentiator. I understand how a small R will produce allow Vc to be ~Vin, for DC. And adding a load will mean that the current across R (not labeled but there) will decrease, and increase Vc. So there is: an output proportional to the rate of change of input.The output proportional to the rate of change of input is dVc/dt in I = CdVc/dt. Here the proportion is times C. Attaching a load, it would be a fraction of I (aCdVc/dt) and then the voltage would be Rload * aCdVc/dt. Correct? And now, I imagine there are mA to uA and a resistor of 100k to get some voltage drop. Thinking quickly to get help, I’d love to know the uses of an output proportional to the rate of change of input and if this is how that output is used (i.e. Rload * a*CdVc/dt).Kind of a tangent: a while ago I considered using an integrator to produce an LED that glows brighter.

author: rstofer
author_rank: Super Contributor
timestamp: October 24, 2019, 01:52:52 am
content: Differentiators are avoided, but sometimes used, for analog computing.I used to see clock pulses created by differentiating a square wave and keeping just the positive going edge. This was done a long time ago when the square wave was used to gate a signal and the edge was used to latch it.Otherwise, these differentiators are nothing more than high pass filters.It remains to be seen if the derivative of a sine wave is equal to a cosine wave. i think there will be some fiddling around to find the proper values.

author: pwlps
author_rank: Frequent Contributor
timestamp: October 24, 2019, 01:00:34 pm
content: Quote from: renzoms on October 23, 2019, 10:02:47 pmJust replace R by R||Rload in the calculations. So actually your "a" will be a=R/(R+Rload).

author: rstofer
author_rank: Super Contributor
timestamp: October 24, 2019, 04:40:51 pm
content: In the case of differentiating a sine wave, we expect a cosine. So, I grabbed some values out of thin air and stuffed them into LTspice. Output attached.Because there is no initial condition, the very beginning of the waveform is not correct. By 90 degrees, everything is pretty close to correct. The values aren't exactly right but close enough to show the effect.ETA: As a consequence of requiring dVin/dt to be much larger than dVout/dt, we can assume that the output voltage will be considerably less than the input voltage because the dt in both cases is the same. Therefore, dVin must also be much greater than dVout.ETA(again): A value of 10k is probably a better match. In order to get 90 degrees of phase shift, the input frequency must be MUCH less than the 3dB cuttoff frequency of the high pass filter.https://www.electronics-tutorials.ws/filter/filter_3.html
Difficulty in VReg selection - Page 1
Forum section: electronics / beginners

author: aurmer
author_rank: Regular Contributor
timestamp: October 28, 2016, 07:52:31 am
content: My Mouser search powers are failing me. Or is my ELEN 101 why I fail?? What type of Voltage Regulator am I looking for with these requirements? I started with looking LDO Vregs, but all I was finding were ones that change Vout based on Vin. Does such a thing exist?Requirements:Iout: 150mA sustained (even 100mA sustained?)Vin: 3.3V - 5V (as low as 3.3V isn't realistic, but trying to go as low as possible for 'acceptable Vin' because backup battery is 3 AA cells. The lower it will accept power, the longer it can run on battery.)Vout: 3.3V - constant across Vin range.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 28, 2016, 07:57:01 am
content: LDO's wil always drop some voltage. And they often turn off when Vin < Vout+1.You could use a buck-boost regulator. Such as: TPS63060.