# Questions tagged [differential]

Differential refers to any kind of signaling where the signal information is carried by two or more paths and both are required to properly reconstruct the signal. For example, USB D+ and D-

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### How to get the difference between two currents by using only analogue circuitry?

If I have two current sources, producing currents I1 and I2, respectively, getting the sum of the two currents is easy—just connect both sources to one end of a wire and the currents will be forced to ...
43 views

### Should I cut away the ground pour above a diffpair on the first inner layer, which are Z-matched to the ground layer (L2)?

I'm routing diffpairs on the 1st inner layer of a 4-layer pcb which are Z-matched to the 2nd inner layer which is entirely a ground pour. The top layer has traces and routing AND also a ground pour ...
34 views

### What is the expected output of an LVDS IO cell of an FPGA (or just simulation) when the P and N pad inputs are both the same logical value?

I am curious what, in general, the output would be of an LVDS signal when both inputs are the same voltage level. So if the truth table is: ...
86 views

### Differential amplifier IC vs op amp with resistors to make it amplify a differential signal

What is the advantage of using a differential smplifier IC instead of using a normal op-amp and designing the resistor network around it? The ICs seem to be more expensive and require more power. ...
139 views

### What would cause an ADC to stick on an arbitrary value?

I have a differential ADC (HX710) that I am using to interface a load cell. The wiring is as follows with (J4) going to the load cell: Mostly, this reads very reliably and accurately. However, ...
44 views

### How to do multichannel ADC data logging

I need to build a system to monitor several (around ~20) voltages over several days. The ~20 voltages need to be measured differentially. Something which could in theory be accomplishes with 3 of ...
74 views

### Decode rs-422 without line reciever

I have a encoder on a dc motor that outputs it's signals as RS-422. A, ~A, B and ...
95 views

### Single ended to differential driver low-pass filter

I am taking a single-ended source, using a SN75ALS191 driver to convert it to a differential signal. This differential signal will travel over twisted pair cabling several hundred feet, to a single ...
57 views

### Length-matching microwave differential traces

I'm driving an RF mixer that takes differential input signals. My max signal frequency is $6\,\text{GHz}$. I understand that the differential input signals need to be length-matched, but what sort ...
153 views

### How to calculate gain of wheatstone bridge+differential amplifier? [closed]

Can someone help me solve this task? The schematic shows that the sensors are connected in series parallel and that the measurement is done using a Wheatstone-Bridge and a difference amplifier. A) ...
84 views

### Measuring current, instrumentation or differential amplifier?

I want to measure current at the high side of circuit with 0.1 mV accuracy using a 16 bit ADC. for sensing the voltage drop over a 100 mΩ 1% resistor I need to use an op amp which is cheap and easy to ...
70 views

For example I have a 10 bits ADC，which has a reference voltage of 2.5V. In single-ended mode,the input range 0-2.5V according with conversion result 0-2*e10. And what about the differential mode？ I ...
37 views

### Understand MIPI-CS2 camera connector on ZYBO Z7

Please take a look at page 2 and page 11 of this datasheet. Why do they bridge the MIPI signals of the connector J2 with a 150R resistor and connect the signals with the FPGA and additional connect ...
114 views

### Do I need a “full differential” ADC? (if sensor voltage input range = 0.8V to 4.3V)

I am not using potentiometer like most video or print online. I am using bike grip/hall throttle, its range is 0.8V to 4.3V. Instead of: [0V = 000 ADC value] [5V = 255 ADC value] I want: [0.8V = ...
102 views

### Differential pair output voltage formula derivation

I am trying to get to the simplified form of the equation of the differential output voltage of a differential pair: I know the correct equation is: *Image above from Franco, S. Analog Circuit ...
76 views

### Should I use a differential mode amplifier for mixing up to four stereo signals together?

I'm designing (probably over-designing, but I want the experience) a four-input, four-output, stereo mixing setup for my PC setup, but I'm concerned that just tying all the ground lines from that many ...
48 views

### Trace width for breaking out 100Ω differential microstrip from 0.5mm pitch BGA

See bottom of post for the actual questions First, some context: I'm making a DisplayPort switch as a hobby project DisplayPort's high speed lines require 100Ω ± 10% differential impedance, which I'...
725 views

### Long-tailed pair - gain and bandwidth

I'm trying to understand this schematic of this differential probe: I marked some blocks. I have some questions about the block I marked "Long-tailed pair" (LTP). I have no experience with LTPs so ...
214 views

### Grounded coplanar waveguide differential gap

I'm driving an ADL5802 RF mixer with a 5400BL15B050E RF balun. The balun turns a single ended signal into a differential signal on balanced lines for the mixer. In my attempt to match the balun ...
38 views

### Mux switching one leg of differential signal

I found the schematic below for a muxed thermocouple circuit from this web page. This circuit uses a mux to switch just one leg of the thermocouples. While I am sure that this works fine I have a ...
32 views

### Diff Op-Amp in current measurement ignores input [duplicate]

I'm working on a small project which involves current measurement. I'm using R10 to measure Voltage drop (100 mV) when 10 mA current goes through it. Next I'm amplifing that signal around 37 times ...
270 views

### Why is 50ohm sometimes used as a differential impedance?

I'm creating a design where I convert an RF single-ended signal to a differential signal with a 5400BL15B050E RF balun that is then fed to a ADL5802 RF mixer. The balun datasheet specifies the single ...
98 views

### Differential Op-Amp Input Voltage

I want to use a rail-to-rail op-amp as a differential amplifier. The op-amp is supplied by 3.3V and the input signals swings from 0 to 5V. I want the output to swing between 0 and 2.5V. My ...
140 views

### Can twisted pair replaced by two wires which are closely placed?

If I have differential signal wires, can I place two wires closely 1mm-2mm gap between them but not twisted? (1mm or 2mm gap is fixed it won't change from place to place ) I am using Differential I2C ...
43 views

### Differential signals passing within 6 mils of ground vias?

It's puzzling I couldn't find the answer to this in the top 3 pages of google results. I've got 4 DIMM240's routing to a single LX150 fpga. Crowded in other words. I'm supposed to keep 20 mils from ...
15 views

### Measuring analog voltage from multiple differential input causes voltage fluctuation

As shown above i am using a micro controller's differential input to measure the analog voltage. When the the micro controller measures the voltage on the input pins there is a voltage fluctuation ...
139 views

### Do I need a common ground wire for differential voltage measurement?

I'm using this module as a digital scope and function generator. I don't have experience with differential measurements(besides multimeters) and I'm wondering do I need to couple a ground wire between ...
61 views

### differential amplifier ac equivalent circuit

In figure a, $R_E$ is clearly in series with the base emitter reisistance $r_e'$ of $Q_2$. But in figure b, why are they putting $r_e'$ in parallel with $R_E$?
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### Altium - Impedance in Signal Integrity and DRU differ

I'm desinging a very simple 4 layer board with a USB connection. I defined an impedance of 90 Ohms (differential) in the layer stackup. This gave me a track width of 0.3 mm with a gap of 0.334 mm, ...
171 views

### Nonlinearities in Fully Differential Op Amp

I am trying to construct an amplifier circuit using a fully differential op amp (THS4503) to interface with an ADC (ADS5232). I will be reading a 0-5V sensor, which needs to be converted to a 1Vpp ...
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### Differential Amplifier, what is the purpose of extra emitter resistors?

I am curious about this differential amplifier circuit: What is the purpose of the two R'E resistors? I know that the big RE acts as to help set up the current source for the DC Q-points, but I have ...
168 views

### Differential RC filter

I sometimes see differential filters like this: And sometimes this : Basically sometimes there are 3 caps (2 going to ground on each input), sometimes I only see 1 cap ( 1 differential cap, none ...
460 views

### Alternatives to RJ45 ethernet connections?

I have a system where two boards need to communicate through a serial bus with several lines --- rates are in the order of up to 3MHz. The boards will be several meters away (say, 3 to 5 meters / 10 ...
83 views

### Design of Fully Differential OTA Circuits

This is the equivalent model of an ideal single-ended OTA: Now, this is the equivalent model of an ideal fully differential OTA: Now, is there a rule for getting a certain circuit with a fully ...
87 views

### Replacement 100 ohm resistor for differential scope probe? [closed]

I'm trying to use a P7504 (\$) "TriMode" scope probe, and unfortunately the resistors eventually break. Does anyone have recommendations for a 100ohm resistor that would replace the ones on the probe?...
47 views

### Differential input circuit design frequency issue?

The current design for this differential op amp scales down -/+ 10V 100kHz signal inputs to 0-3.3V for an ADC to properly read. Using a gain of .165, it adjusts -10 to 0 by adding a 1.65V offset, as ...
829 views

### Terminating Resistors on Ethernet Port

I'm using Ethernet (CAT5/5e/6) cables to communicate with the PCA9615 Differential I2C buffer. These cables roughly have a characteristic impedance of 100 ohms, but I have a few questions about ...
377 views

### Best method to drive SPI over 1 m

In my current project I need to control 8 analog multiplier. They are controlled with SPI but without the MISO line, so I would need to route : SCK MOSI 8 slaves selects So 10 signals in total. The ...
89 views

### How to control microphone-speaker connection between two SIM800Ls with a GPIO terminal?

There is a device consisting of two SimCom SIM800L quad-band GSM/GPRS modules and controlled by an MCU, presumably ESP8266. The idea is to let the first SIM800L call one person, the second SIM800L ...
72 views

### MOS working point in a differential analog mixer

let's consider this simple configuration of a balanced differential mixer (analog multiplier): I have understood that the local oscillator is generally a high signal, while the radio-frequency signal ...
2k views

### How do we explain the common-mode feedback in an intuitive way?

There are such beautiful circuit ideas that make you hold your breath and admire them silently. Such an idea is the common-mode feedback (CMFB) in fully differential amplifiers. I was not familiar ...
371 views

### Negative voltage on both inverting and non-ínverting inputs of a differential amplifier gives non-zero output

I used an LM324 op-amp for my differential amplifier, in which the inverting input voltage is constant and the non-inverting voltage varies between the range -1.30 V to 1.30 V. I am having an issue ...
44 views

### Can I directly connect microphone to speaker of two SIM800Ls

There are two SimCom SIM800L quad-band GSM/GPRS modules. I would like to make some kind of call relay, such that SIM #1 accepts incoming call, then SIM #2 executes outgoing call, and once both ...
65 views

### What type of MUX to most effectively connect both sets of resistors at once?

The following circuit is used PER CHANNEL, and I have 4 channels, to according scale the gain for our input signals on each channel. However, each channel, has to be able to switch between 4 ...
87 views

### Doubts about a differential negative resistance oscillator

let's consider this kind of differential negative resistance oscillator: The output of this circuit is VA - VB. My book says the following sentence: From a quick analysis of the circuit it can be ...
3k views

### Can anyone explain this balanced driver circuit to me?

I'm looking to generate a differential signal to control a laser projector's galvos, and as I understand it needs to be +5V/-5V (10Vpp). I've found this circuit for a laser harp, but I'm confused ...
1k views

### Is the ground necessary with an opto-isolated RS422 signal

I have 8 opto-isolated RS422 ports to install. All of them are coming from a single PC card. It provides the opto-isolation for every RS422 port. Every signal is opto-isolated from the PC ground and ...
340 views

### Swapping out RJ-45 connector on Differential I2C circuit

I'm trying to use Sparkfun's Differential I2C Breakout circuit into my own design, and I'm looking to replace the RJ-45 connector. It's too big (having a footprint size of 15.24 mm x 15.24 mm), and I ...