LTSpice, better way to generate differential signals?

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cspwcspw

Joined Nov 8, 2016
78
Hi - I'm trying to understand an instrumentation amplifier that starts with a differential input with a common-mode DC offset voltage.
So I'd like, say, my inputs to be 100mV sin wave with a DC offset of 1V. Generating this with a Voltage source is easy, but then I only have a "single ended" voltage source. I came up with an ungainly plan, but I'm hoping someone can show me a more elegant way to do what I want. My plan was to have to independent voltage sources driving the two differential inputs. Both use identical common offset voltages, frequency, and contribute half my desired amplitude. The phase on one leg is offset 180 degrees. Its an ugly LTSpice hack. Is there a nicer way to get a 2-ended sine wave generated, centered around a common DC mode voltage? Thanks1607317384183.png
 

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crutschow

Joined Mar 14, 2008
27,220
Since sources can float, here's an alternate way that allows easy, independent adjustment of both the differential and common-mode signals, with either being AC or DC:

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