9/25/2023 0 Comments Voltage follower op amp![]() ![]() This goes against our human intuition that is why I suggest you to see again the meters' readings or hover the mouse over the circuit nodes and elements so you can see for yourself. But since still there is no load connected, no current flows and the output voltage is still equal to the input voltage. Also, an imperfect ammeter can have an internal resistance RA = 1k (we can set it in the ammeter CircuitLab parameters). For example, a real (imperfect) input voltage source RVS (in a purple frame, in the schematic below) or the line can have an internal resistance Ri = 1k (we can present it by a 1 k resistor Ri). ![]() In electronics, we work with real elements that have some resistance. In life, however, something always appears that prevents us from realizing our intentions - for example, we are weak or sick to do it, and the result is less than expected. Simulate this circuit STEP 3: Disturbed "wire follower" So the output voltage is equal to the input voltage (see the meters or hover the mouse over the circuit nodes and elements to see for yourself). It works fine since there is no disturbance - the voltage source is "ideal" (with zero internal resistance), the wire is an "ideal" conductor (with zero line resistance), the ammeter is "ideal" (with zero internal resistance) and there is no load connected (open circuit). In electronics, the first idea that comes to mind is to connect a piece of wire from the input source to the output. In life, the obvious solution is to get down to business and solve the problem ourselves. ![]() Simulate this circuit STEP 2: "Wire follower" In electronics, such a task is "voltage copying" - we want the same output voltage Vout as the input Vin1 to appear in a different place (the output). Simulate this circuit – Schematic created using CircuitLab This is a kind of "active copying" - we have some goal X in our head and want to materialize it as Y = X. We can see it all around us and we ourselves behave according to this idea when accomplishing our goals. The op-amp follower is a simple circuit based on a great idea that is not just electrical. I will reveal the circuit idea in the following sequence: non-electrical examples (analogies), passive electrical circuit, man-driven circuit, op-amp circuit. I will do it in a scenario of five consecutive steps illustrated by CircuitLab simulations with each subsequent step building on the previous one. The best way to show WHY a circuit is made that way is to build and "invent" it step by step. If we do not do this, those to whom we explain will know the circuit but will not understand it. To explain a circuit, we must show not only WHAT and HOW but also WHY it is made that way. I've checked a couple of books and the internet, but every source just tells me it's a voltage follower, and not why. More here: How is op amp output not zero if inputs have the same voltage?Ī slightly deeper, but very accessible paper here:
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