analog connection for converting single ended to differential - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: May 25, 2025, 09:10:00 pm
content: There is a circuit I built which inputs a differential and outputs differential present in Ltspice schematics. I want this circuit to input a single ended signal. Is there some active component or certain active configuration with this component which will transform single ended AC signal into differential signal? Thanks.

author: MF-jockey
author_rank: Regular Contributor
timestamp: May 25, 2025, 11:10:22 pm
content: Often a suitable transformer is used.Which signals should be converted?

author: John B
author_rank: Frequent Contributor
timestamp: May 26, 2025, 03:12:39 am
content: Fully differential amplifiers. They have 2 inputs for a differential input signal, but you can just as easily ground one input and apply the single ended signal to the other. For audio I use the OPA1632The bonus is that you can swap your ground and signal to invert the phase of the differential outputs. It's handy if you have some inverting configurations in the signal chain beforehand.

author: mawyatt
author_rank: Super Contributor
timestamp: May 26, 2025, 12:25:36 pm
content: Here's something that may be of interest, it's a Single Ended Input to Class A/B Differential Output Amp.https://www.edn.com/single-supply-single-ended-input-to-pseudo-class-a-b-differential-output-amp/https://www.eevblog.com/forum/projects/single-to-diff-output-amp-with-single-supply/msg5552693/#msg5552693https://www.eevblog.com/forum/projects/interesting-amplifier-topology/Best

author: Terry Bites
author_rank: Super Contributor
timestamp: May 27, 2025, 07:10:42 pm
content: There is a simpler way of course. See atatched. The accuracy of the conversion depends on the opamps and the resistors.You can go to town with 0.1% jobs or use an array. The initial tollerance isn't all that but you usually get good matching on the cheap.A ready made fully integrated (pricey) version of this is an LT635. I'm sure there are others out there in the aether."Fully differential amplifiers" work great and they're not expensive. They are intended to drive ADCs from an SE source."ADSL line drivers" are the truly brutal form of these if you need serious drive capability.You may need a buffer and that also gives you oportunities to add gain and bandpass limit.Seehttps://www.analog.com/en/resources/analog-dialogue/articles/single-ended-to-differential-signal-conversion.htmlandhttps://www.analog.com/en/resources/analog-dialogue/raqs/raq-issue-161.htmlHave you looked into "audio line drivers" A THAT1646 for example. This SE to diff is exactly what they are deisgned to do.They will do the conversion and also actively control common mode voltages at the output.Though active control isn't needed unless you need to drive a long line with uncertain balance of the termination impedance.also seehttps://sound-au.com/articles/balanced-io.htm

author: mawyatt
author_rank: Super Contributor
timestamp: May 27, 2025, 08:26:41 pm
content: Actually even simpler with what's shown in the schematic above. You can eliminate the input follower amp as the input signal voltage source is in parallel with Rin, thus Rin has no effect.Just simply connect the Vin source directly to the inverting amp R2 and use Vin as the + signal the inverting amp output as the - signal for differential output!!Best

author: David Hess
author_rank: Super Contributor
timestamp: May 27, 2025, 11:47:26 pm
content: Traditionally various discrete phase splitter arrangements were used.A pair of instrumentation amplifiers can convert single-ended to differential by connecting the input signal to the inputs, but reversed on the second instrumentation amplifier. I do not remember where I saw this.A cross-coupled single-ended to differential converter is shown below.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: May 28, 2025, 03:11:24 am
content: I remember a couple old ICs that did this, PMI SSM2143 receiver and SSM2142 driver. Obsolete but the data sheets are still out there with the block diagram of how they work.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 28, 2025, 06:46:57 am
content: A typical case for the single ended to differential conversion is driving an ADC with differential input. This usually does not need perfect symmetry, just a stable overall gain. The ADC usually have at least reasonable CM suppression. So there is limited need for super accurate / well matched resistor values.