Say I have a signal driver operating at 50 ohm output impedance, driving something with high (hundred kilo-ohm) input impedance. If the wavelength I'm using (a few kilohertz) is much longer than my chord length (a couple feet), then I understand that standing waves cannot develop..
But, do I need to worry about the reflection causing damage to my driver? I guess a back-reflection always occurs if you have an impedance mismatch. Why do we usually only worry about this sort of thing when standing waves are possible, typically at 'high' (RF) frequency?
Best Answer
One starts to worry about reflections at high frequency because the disturbance caused by such reflections (which are high frequency as well) will interfere with the signal. At low frequency, the first capacitor down the road will filter those disturbances out.
Reflections may happen regardless of the useful frequency of the signal. If the signal happens to have sharp edges (short rise / fall times), you may end up with twice the voltage at the end of the line.