The non-inverting op amp high-pass filter (first picture below) has a unity gain limit close to DC, while inverting op amp high-pass filter (second picture below) doesn't have such a limit. So why do people still use the non-inverting high-pass configuration?

enter image description here enter image description here

  • \$\begingroup\$ shva, are you sure that the primary purpose of the shown circuits is high pass filtering? I ask this because both circuits are based on the classical principle for providing a suitable bias point in case of single supply. IMO it is very uncommon to use such an opamp based circuit for a first-order filtering. In addition, the circuits provide a very "bad" highpass filtering. \$\endgroup\$ – LvW Mar 14 '16 at 16:15
  • \$\begingroup\$ The first circuit is a shelving filter, not an HPF \$\endgroup\$ – endolith Sep 9 '16 at 13:52

There is a reason non-inverting 1st order high-pass filters are sometimes used and this is to preserve the dc level in the circuit. It's horses for courses - some designs will want to preserve the DC level, some won't care and some won't want to. It's not a black and white sort of thing.

When it comes to a 2nd order high-pass filter the non-inverting configuration (Sallen Key type) will usually be preferred and this doesn't preserve the dc level: -

enter image description here

Again horses for courses.

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  • \$\begingroup\$ Some interesting euphemisms there Andy! \$\endgroup\$ – KyranF Mar 14 '16 at 15:46

Here they talk about it. Several points they raised were:

unlike a non-inverting OP-amplifier which has a minimum possible gain of 1, an inverting Op-amp can be used as an attenuater with a gain less than 1 as well.


input impedance of non-inverting op-amp is infinite while that of Inverting op-amp it is equal to the resistance between the input and the inverting terminal, so a better impedance matching can be obtained.

This site has good scope outputs to show you more info, and they sum it up by:

the bandwidth response of an inverting amplifier is better over a longer range. That means that you could use the amplifier with a better range frequencies of input signals.

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  • \$\begingroup\$ Quote 2 is tortuously close to irrelevant (I'm trying really hard to think of a circumstance when this opportunity may be valid). Quote 3 means what exactly? What is bandwidth response? What is a better range of frequencies? \$\endgroup\$ – Andy aka Sep 14 '13 at 18:01
  • \$\begingroup\$ Also, you first quote is from a question that relates to non-inverting amplifiers without a mention of it being a filter. This then becomes a misleading answer in my opinion and because the OP has accepted an answer that is basically flawed on all three quotes I have to down-vote so that others coming along later may not be as easily persuaded it is a decent answer. \$\endgroup\$ – Andy aka Sep 14 '13 at 18:33
  • \$\begingroup\$ The gain-bandwidth product of an op amp doesn't differentiate between inverting and non-inverting amps as far as I'm aware so how can an inverting amplifier give a better frequency range response? en.wikipedia.org/wiki/Gain–bandwidth_product \$\endgroup\$ – JIm Dearden Sep 14 '13 at 18:40
  • \$\begingroup\$ How about the fact that the answers are out there... a simple search showed few relevant answers. No need to bash at me for "quoting" \$\endgroup\$ – KingsInnerSoul Sep 14 '13 at 20:55
  • \$\begingroup\$ @Andyaka Wanting a filter with a high input impedance is common to avoid modifying some previous stage, introducing distortion, etc. However the input impedance of a non-inverting filter is not infinite, as it says. For a Sallen Key lowpass filter it drops with frequency, for instance. \$\endgroup\$ – endolith Sep 9 '16 at 13:54

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