# 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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### Common mode RC filter of High-BW differential line

I'm using a fully differential analogue chain, using 20Hz HP, 3MHz LP and x2 Gain. My signal of interest is fully differential with a 200KHz fast modulation and a 100Hz sawtooth ramp. The high ...
720 views

### Why is a reference plane needed in differential signalling?

As I understand differential signaling, return current goes via the "-" (minus) line, so why we do we need to provide a reference ground plane for differential signals?
468 views

### What mathematical equation can be used to represent the output of this differential amp circuit?

My lecturer has gave my class a number of circuits to analysis and currently I'm having trouble with the following circuit: I am familiar with how to calculate an equation for the standard ...
396 views

### iCE40 LVDS clock input

I'm trying to figure out how to correctly connect 200MHz LVDS oscillator (DSC1103CE1-200.0000T Datasheet) to ICE40LP1K-QN84 FPGA. After reading Lattice's guide to differential signals (Link) this is ...
250 views

### Current mirror and differential amplifier

Hi, In the attached figure, I am not sure how to formulate the relation between $I_{ref}$ and the DC currents through the four transistors $Q_1-Q_4$, given that $I_{B1,2,3,4,5,6}$ aren't ...
3k views

### Where are small-signal differential amplifiers used?

I am teaching students about the differential pair (see circuit below). I addressed many issues like the difference between differential and common mode gain, taking arbitrary vb1 and vb2 signals and ...
460 views

### Output resistance in a BJT differential amplifier

I have the following differential amplifier and I would like to find which is the output resistance of this circuit in the cases of differential input and common mode input.I know that the input ...
10k views

### Differential analog signal conversion using Arduino Uno

I need to perform a A/D conversion for a differential signal using Arduino Uno. I have tried a software method where I connect one input to A0 and another to A1, read ADC for both channels and then ...
128 views

### Differential equation of circuit which contains R,L,C components

I'm having bit of a trouble finding the differential equation for this circuit. I'm aware of how to construct the equations for simple paralel and series RLC circuits, but in this case the current ...
444 views

### Is there an amplifier voltage limit for the input signal even if the differential voltage is small?

I am building a simple current sensor. The amp says the maximum differential voltage is 5V. I'm not getting more than 1V in differential voltage at the moment. Is it safe to test differential ...
44 views

### Differential Op Amp queston

So we are given the equation: Vout=Rf/Rs(V2-V1) I'm just wondering how would we solve it when the Rf/Rs are different values like they are in this circuit: simulate this circuit – Schematic ...
218 views

### sizing a DC bias RF choke for a differential antenna + PA

Trying to figure an antenna for the Si4012 RF chip. Page 26 of https://www.silabs.com/documents/public/application-notes/AN639.pdf talks about feeding the two sides of the loop antenna through two ...
1k views

### RS485 communication problem

I've designed a board with microcontroller (NXP, K64) to control i/o's. The uart port of the uC is connected to Maxim 3362 which converts the signal to RS485 half duplex communication. Using modbus ...
344 views

### How can I measure differential voltage with ArduinoUNO or UNO32?

First of all, thank you for your time. I need to measure the differential voltage from the temperature sensor Fluke 80T-IR (infrared temperature probe), I need to do this with an UNO32 or Arduino UNO.
700 views

### Difference Amplifier with 3 Op. Amp. How to analyze it?

I have to demonstrate, in the following circuit, that $V_o= \left( 1+\frac{2R_2}{R1}\right)(V_2-V_1)$ if the Pot is in the halfway. I know that the circuit inside the pink block its a Buffer for ...
82 views

### Does differential sending benefit current sensing circuits in the same way as differential voltage sending?

I'd like to send two currents along a long twisted pair (well, ~5m, but I want to be very careful about noise in this experiment). The two currents are produced by two photodiodes with equal and ...
674 views

### Sallen-Key with fully-differential output — options?

I have a single-ended audio signal that I want to low-pass filter and convert to differential (with GND as the OCM voltage — that is, when one output is X Volts, the other output shall be −...
401 views

### Confusion about the use of AIGND in a differential amplifier

Above is a differential amplifier used to measure differential ended signals. Here is what I understand: The amplifier subtracts two input voltages with respect to its measurement ground(AIGND in the ...
123 views

### Should long RF traces be differentially routed?

I'm designing a phased array controller and as such includes a dozen splitters . The board dimensions are approximately around 10 - 11 cm and the RF traces are about 8-9 cm in length . Would ...
860 views

### sending differential signals off board, what kind of connector do I use?

So, my question is this. I've got four differential pairs from an LVDS chip which need to go to a connector, along with a few single-ended signals. For this purpose, I chose a hirose df13 connector. ...
181 views

### Differential encoder output of PSK modulation input

I am a bit confused to the answer given for the following question. The question reads as follows: If the input to a binary differential PSK modulation system is 01100101000111 tabulate The ...
817 views

### Is it possible to switch high speed USB data lines with a MOSFET?

I'd like to programatically disconnect DATA lines on a USB device (while leaving the power lines active), and I know that USB data lines are a differential pair, which I have no previous experience ...
3k views

### Amplifying an audio signal with an op amp

I'm trying to build a pretty basic color organ, but i ran into a problem and I can't seem to find the solution to my specific problem. I built this circuit (using a 3.5mm jack connected to a phone or ...
531 views

### Can I just use one end of a differential op-amp ? (ie use differential op-amp as a single ended op-amp)

I found this awesome op-amp I can use which is super cheap and super fast (NE592D). Unfortunately, it has differential inputs and outputs. I can probably deal with the differential inputs, but how ...
141 views

### Circuit for connecting externally power instrument to MCU

I have externally powered instruments that I need connected to the ADC inputs of an MCU. They output 0-5V analog, and the MCU accepts 0-3.33V. There is no guarantee of the voltage difference in ...
2k views

### Use transistor to connect terminating resistor for differential signal?

Is it okay to use a transistor to connect a terminating resistor between the A and B lines of a differential signal? I'm not sure because I know that at the source/emitter of an NPN transistor must be ...
3k views

### Differential Voltage Measurement

I've read various posts regarding differential voltage measurements. I'm confused as to why it seems virtually impossible to measure differential voltages that are high relative to ground (like ...
87 views

### What “type” of impedance is a schematic referring to when talking about differential signals?

I'm trying to learn a bit about routing high-speed differential signals. One thing that is confusing me is that often schematics talk about routing certain signal pairs with a specific impedance (...
2k views

### Differential Signals - Why is having an equal impedance an advantage?

I lately heard in a course that a main advantage of differential signals is that both signals show the same impedance, whereas a single-ended signal, which is measured against ground, has a high ...
1k views

### Capacitor between grounds: Reason and how to decide the value

while going through the reference designs, I came across the capacitor between grounds. Is it for RF noise protection? Is ground for U4 and other part of the circuit is different?
446 views

### problem with differential amplifier output ..not getting expected voltage at output i.e( V2-V1)..what is wrong here?

i have made the following differential amplifier but facing problem with this differential amplifier here i am expecting 7v i.e.(V2-V1) at output but only getting 4.999V .what is wrong here ?
1k views

### Voltage Swing in Differential Signal

My Doubt is in voltage swing of a differential signal. Here is the scenario :- The voltage swing of LVPECL is 800 mV. Assume it as my driver. So, in case I want to drive an LVDS input, I would go ...
176 views

### AD8131 Single Ended to Differential Problem

I am attempting to convert a single ended signal (0-5V) to a differential signal (+/- 5V about 0V) using an AD8131ARZ. I have it wired as per the attached schematic. When I supply +5V to the positive ...
319 views

### Measuring current transducer output - differential or single ended?

I'm designing a front-end for an ADC that will be measuring the voltage of a hall effect current transducer. I have been reading up on differential vs single-ended measurement, and have become a bit ...
199 views

### Art Of Electronics - RC Differenciator Circuits and High Pass Filters

In the above image, take note of the line dV/dt being much less than dVin/dt as a condition. I once asked a question about Integrators. I understand both the above image and my earlier question on ...
59 views

### 2nd order differential circuit, converting to S

when converting to S domain, the general rule (1/LC)i = 2*t* how come this does not equal to 2*i* just like (1/LC)iL = 2*i*L? thanks in advance for any help
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### BJT Differential Amplifier deliberately saturated?

Happy New Year! I've recently completed a metal detector project (see my recent questions) and I've been going back over some of the parts I didn't fully understand first time around. This question ...
4k views

### Differential-output op-amp vs. additional inverting op-amp?

I'm wondering what the real advantages of op-amps with differential outputs are (e.g., AD8138), compared to just taking a signal V+ and feeding it to a unity-gain inverting amplifier to obtain a ...
4k views

### Differential amplifier with differential output and common-mode shift

Summary: I would like to build a differential amplifier with differential output, but shift the common mode to a different level from the original. My current knowledge takes me this far: Take the ...
202 views

### Floating inputs and Vref on a voltage subtractor (PWM to Gate converter)

A little background: I'm trying to extract a gate signal from someone else's circuit (ckt1) so that I can synchronize events in my design (ckt2) to a sequential trigger in theirs. First problem is I ...
7k views

### Maximum slope of a sine wave

For a signal with amplitude, $$V = A\sin (\omega t)$$ any idea at what point the maximum slope (gradient, dv/dt) is? I have gone through the method of differentiating which yields A\omega \cos(\...
1k views

### Differential gain of amplifier with current mirror and NO LOAD

Please consider the differential amplifier (Q1&Q2) with current mirror active load (Q3&Q4) as shown below: simulate this circuit – Schematic created using CircuitLab I know many ...
2k views

### Differential voltage to current converter

I have this circuit to solve: with $R_2=R_3$ and $R_4=R_5$. I want to find the transfer function between $I_{\text{out}}$ and $V_{\text{in}}$ (differential). I'm trying to use superposition, ...
189 views

### What's the point of board-internal differential pairs?

Sorry if this is an ignorant question. But I just can't fathom what the advantages are of using a differential pair for signals not leaving the PCB. I mean, the usual argument for using a ...
177 views

### Interfacing to a differential signal with isolation

For diagnostics I need to monitor a differential data signal similar to RS485. For safety the signal need to be fully isolated. The thought that I had was to use a pair of opto isolators across the ...
898 views

### CML/LVDS driver for several GHz, parasitic RC filter formed by terminating resistance and load capacitance

Update: Based on useful comments of The Photon, Andy aka and PlasmaHH. As I got, there is indeed the parasitic low-pass. There is no magic bullet that will mitigate it. Large receiver capacitance is ...
482 views

### Choosing proper CCS current for discrete transistor amplifier's differential and VAS stages

Here is a figure from "Audio Power Amplifier Design" by Douglas Self. Self using almost same current values (4mA and 6-8mA) in many examples without explanation. How to choose these values properly ...
349 views

### how does negative differential resistance in a PCT work?

I understand that up until a point (Vforward), the differential resistance is positive. And then it turns negative, and as the voltage increases, the current decreases, as you can see in this IV curve ...