A Precision Polarity (Phase) Inverter Using the THAT1240

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mediatechnology
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A Precision Polarity (Phase) Inverter Using the THAT1240

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Here's another installment in the THAT1240 circuit collection. It's a precision polarity inverter that is a variation of the Graeme, Jung et al "phase flippers." What makes this one unique is the use of the THAT1240s precision matched internal resistors for gain setting. This assures dB accurate inversion so that comparisons made between something "in phase" and "out-of-phase" are not influenced by level.

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The value of the 10K is not critical but the driving source impedance must be low. In my tests the 50 ohm generator output level changed by ~0.10 dB as a result of changes in loading between normal and inverted polarity. This stage must be driven by an op amp. Once I factored out the change in level due to loading I observed less than 0.01 dB change. I must admit that this was the resolution of the instrument so suffice it to say the ultra-precise matching of the THAT1240s internal resistors make for a simple cost-effective circuit.
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