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Hi,often using inverting or non-inverting does not really make any difference. But in some instances it does. Does anybody have a summary of pros and cons of the two configurations? From simple things like gain (R2/R2 vs 1+R2/R1) to input impedance to noise levels to the fact that inverting can be used as a mixer etc. etc.?We could compile a list here then I can summarise all points at the end into a downloadable PDF for anybody to download.Many thanks
Inverting, according to Jim Williams, has lower input distortion because the input circuit is kept close to a constant value. Therefore less overall distortion.
Been there done that, Op amp noise is calculated using non-inverting math, you don't get a free lunch no matter the architecture, https://www.analog.com/en/analog-dialogue/articles/op-amp-issues-noise-gain.htmlInstead you have to get creative with what you can alter,
The inverting configuration is more stable, than non-inverting, because it has a higher noise gain. An op-amp which is only stable down to a gain of 2, in non-inverting configuration, will be unity gain stable, in the inverting configuration.
The main downside to the inverting configuration is noise. For a reasonable input impedance, there is a resistance of that value in series with the input signal, with associated thermal noise. The non-inverting configuration can present lower resistance to the op-amp inputs. One interesting possibility to avoid common-mode problems is to connect a floating source (such as a phono cartridge) between the feedback network and the inverting input, with the non-inverting input grounded. This is rarely done, since it requires a truly floating source.
Quote from: TimFox on February 14, 2020, 06:05:58 pmThe main downside to the inverting configuration is noise. For a reasonable input impedance, there is a resistance of that value in series with the input signal, with associated thermal noise. The non-inverting configuration can present lower resistance to the op-amp inputs. One interesting possibility to avoid common-mode problems is to connect a floating source (such as a phono cartridge) between the feedback network and the inverting input, with the non-inverting input grounded. This is rarely done, since it requires a truly floating source.Yes that's true, although the current noise from the op-amp is often more of a factor, than the thermal noise from the resistor, especially with bipolar input op-amps.
Quote from: Zero999 on February 14, 2020, 07:19:46 pmQuote from: TimFox on February 14, 2020, 06:05:58 pmThe main downside to the inverting configuration is noise. For a reasonable input impedance, there is a resistance of that value in series with the input signal, with associated thermal noise. The non-inverting configuration can present lower resistance to the op-amp inputs. One interesting possibility to avoid common-mode problems is to connect a floating source (such as a phono cartridge) between the feedback network and the inverting input, with the non-inverting input grounded. This is rarely done, since it requires a truly floating source.Yes that's true, although the current noise from the op-amp is often more of a factor, than the thermal noise from the resistor, especially with bipolar input op-amps.When current noise is important, it will flow through a larger resistance in the inverting case than in the usual non-inverting case, where the source resistance from the feedback network is lower than the inverting-case input resistance, for a reasonable input resistance. This will still make more noise voltage than in the non-inverting case. The big problem with the non-inverting case is still common-mode distortion.