The Op-Amp Integrator, Revisited | Op-Amp Basics, episode 10

The Op-Amp Integrator, Revisited | Op-Amp Basics, episode 10 Please help me in supporting Médecins Sans Frontières | Doctors without Borders https://events.doctorswithoutborders.... In this episode, we take a deeper dive into op-amp integrators, and how they expose the flaws of the underlying op-amps. We learn of two major issues they expose: input bias current, the tiny current that op-amp inputs draw, and input offset voltage, the tiny voltage difference that must be cancelled at the op-amp inputs in order to get zero voltage at the output. We learn to correct input bias current by equalizing the impedances seen looking back in the circuit from the two op-amp inputs. We learn to manage offset voltage by applying offset trim (for op-amps that offer it), or by choosing an op-amp with intrinsically lower offset. Finally, we learn about auto-zero op amps, which use a clever technique where a second op-amp alternates from nulling its own offset and nulling the offset of the main op-amp. We put together everything into an integrator both sensitive and stable enough to measure the shaft position of a tiny electric motor over a period of many seconds. 00:00 Introduction 01:26 Review 03:32 PSA 05:31 Building with LM741 06:39 Input bias current 08:23 Input offset voltage 09:19 Equalizing input impedances 11:56 Trimming the offset 13:25 FET inputs - near-zero bias current 14:24 FET thermal stability 15:47 The auto-zero op-amp 21:07 Auto-zero advantages/disadvantages 22:23 Example auto-zero amp 23:44 Auto-zero noise 25:20 The integrator torture test 28:44 Summary and next steps Music: “Light Sting” Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 4.0 License http://creativecommons.org/licenses/b... © 2025 Kevin B. Kenny