high input impedence and buffer

[davyzhu]

Hello,

I found a sentence " The Op Amp has high input impedance, this mean that its input are buffered". As far as I know, buffer means large current, but high input impedence means little current, am I right?

Davy Zhu

 

[nicleo]

I found a sentence " The Op Amp has high input impedance, this mean that its input are buffered". As far as I know, buffer means large current, but high input impedence means little current, am I right?

Due to its 'high input impedance' and 'low output impedance', Op Amp can be configured as a buffer (e.g. voltage follower). As the input impedance is high, current flows into both terminals is very little. Since the output impedance is low, loading effect is small though a considerable amount of current is drawn from the output of the Op Amp.

For an Ideal Op Amp,
Input Impedance -> Infinity -> Input current = 0
Output Impedance -> Zero -> loading effect = 0

 

[DarkJedi]

Yeah, buffers usually give more current but at the output, in the input they have little or none current coming to them, that is why it is used when you want no charge effects, no input current, no drop of voltage, yet you can draw enough current for other aplications from it.

 

[maharshi_qis]

ya..buffers r used to drive high currents ..i.e as amplifiers..