Balancing Resistors Reduce Voltage Follower Common Mode Distortion

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AnalogJoe
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Re: Balancing Resistors Reduce Voltage Follower Common Mode Distortion

Post by AnalogJoe »

The main culprits, in most cases, for CM distortion are reversed biased PN junctions (like BJT colector-base junctions) which vary their capacitance non-linearly as their depletion layer (or region) changes in size as the voltage across the junction also varies, which creates distortion voltages as these non-linear currents flow through resistors. Balancing resistors create equal (or near-equal) voltage drops across the op-amp's differential inputs, which reduces distortion. Inverting amplifiers have near-zero voltage swing at the op-amp's input, hence the junction capacitance remains near-static and almost zero CM distortion occurs. Adding input protection diodes to an opamp amplifier makes the problem worse; Merlin Blencowe discusses some simple but effective solutions.

The article Merlin Blencowe wrote for ED Magazine a few years ago on reducing common mode distortion due to input protection diodes is:

https://www.electronicdesign.com/techno ... p-circuits
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mediatechnology
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Re: Balancing Resistors Reduce Voltage Follower Common Mode Distortion

Post by mediatechnology »

I remember that article. Thanks for linking to it!
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