As the title, what is the role of R3? Why can't the coupling capacitor at the input end be added after removing it, otherwise the oscilloscope waveform will run away.
Terry ポストする October 8, 2020
The non-inverting input terminal of the op amp has an offset current. If R3 is not added, the non-inverting input terminal is equivalent to an open circuit, and its resistance is very large, which will damage the op amp.
Jenson ポストする October 8, 2020
So it can be understood that after R3, the offset current flows into the ground through R3. Will the voltage drop on R3 not damage the op amp?
Elsa ポストする October 8, 2020
Pull down the potential of the same direction terminal to stabilize the input terminal.
Jenson ポストする October 8, 2020
I don't understand how this resistor stabilizes the input terminal?
Is it a stable DC voltage? If the input signal has a DC component, the op amp has infinite input impedance, so the DC bias is all on R3, will it not affect the output signal?
But in this case, why can't there be only one capacitor C2?
Terry ポストする October 8, 2020
In severe cases, it is damaged, and in case of instability.
Elsa ポストする October 8, 2020
Think about the effect if there is electrostatic interference.
