Why is it necessary to connect an impedance conversion op amp? Why is impedance matching necessary. Why does it help common mode rejection?
The impedance matching network says to avoid self-oscillation and reduce high-frequency noise. Always can't understand
So I want to ask the great gods on the forum to tell me about your understanding of impedance matching and some practical uses of impedance matching.
Maia 发表于 December 21, 2020
The reference voltage of the resistor divider is related to the internal resistance without the follower voltage. The addition of an operational amplifier is similar to "isolation"! ! ! ! ! ! ! ! ! ! ! ! !
Freya 发表于 December 21, 2020
It makes sense, so the output of the op amp is approximately a constant voltage source,
I have always questioned the isolation of the follower. Isolation can isolate the external interference, but won't the external interference still pass through the op amp to the output?
Is the external interference superimposed on the signal, and then it will be followed into the output end? Generally, a follower is used to input high impedance and output low impedance characteristics. How to understand this isolation?
Lance 发表于 December 21, 2020
For high-frequency signals, after the signal frequency increases, the high-frequency effects of various components appear, and various components begin to show frequency response, and even local resonance occurs. On the one hand, the harmonics of the signal are universal, but the power is very small compared to the signal. Sometimes the frequency response of the component will have a resonance effect on a certain harmonic of the signal, thereby amplifying a part of the harmonic energy and generating it to the harmonic wave. On the other hand, due to the nonlinearity of the frequency response of the components at high frequencies, this will lead to the appearance of various harmonics and even addition and subtraction of harmonics. Impedance matching can make the impedance of the front and rear stages purely resistive (eliminate the influence of reactance), so that the signal can be transmitted without loss.
Ronan 发表于 December 21, 2020
This connection is a voltage follower, which reduces the output impedance of the signal to prevent the internal resistance of the subsequent stage from causing a voltage divider effect on the front-end signal and causing the signal to shift.
