Current Sense Amplifiers (1/2): Why not to use an OpAmp (CMRR etc.)

Issues with high side sensing, common mode voltage and CMRR … ↓↓↓ Complete description, time index and links below ↓↓↓ First I have a look at a typical high side current sensing application using an OpAmp in differential amplifier configuration. There is also a short excursion why low side current sensing is easier but might not be desirable anyway. Then I go over the limitations (common mode voltage, output swing) and a major drawback (common mode rejection ration) of general purpose operational amplifiers in this application. There’s some talk about dB and logarithm too. 00:00 Intro – there will be a second part 03:49 OpAmp – as differential amplifier for high side current sensing 10:24 Low side current sensing – the undesirable easy way out 12:14 Output swing – it’s either a negative supply or a rail-to-rail device 14:00 Common mode voltage – your positive supply needs to be as high as it gets 16:50 OpAmp differential amplifiers – why the short formula is a lie 21:35 Common mode amplification – the evil twin of differential amplification 24:26 Common mode rejection ration (CMRR) – the measure of evilness 27:41 Decibels (dB) – the engineers’ choice as far as units are concerned 30:41 Back to common mode amplification – from CMRR in dB 35:45 Wrap-Up – coming up next: examples and a live circuit Tutorials: https://www.youtube.com/playlist?list=PLwq-2MnM58FKn3920rc1V0qoTsQDheTIw Year Old Self-Build Analog Multimeter Teardown: https://youtu.be/B_nrExZpGE8 Current Sense Amplifiers (2/2): Examples and Circuit with LT6105: https://youtu.be/FJwgY0ORfp8