Input and Output impedance

[stupen]

In case of transistor if the input impedance is low it will cause 'loading of circuit' and if output impedance is low it helps to 'drive the load'
What is meant by that?



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[RFamateur]

Impedance is essentially an elements resistance to AC power. In the case of transistors, when you have a low input impedance and a high output impedance it is usually evidence of a voltage amplifier, or common-emitter configuration.  On the other hand high input and low output impedance tends to produce current gain (tends to be common-collector).  With equal impedances you tend to produce power gain and is usually called a common-base configuration in transistors.  The last configuration isn't used too much but it is used in RF amplification :D.

RF

[Hero999]

I wouldn't advocate trying to help those with spam in their signatures.

[Kevin Weddle]

Loading of a device means lowering the resistance of the load. But if the transistor circuit is designed with low value resistors, then a medium resistor load will not affect it much.

[audioguru]

Why not use an opamp? Its output impedance is almost zero.

[Hero999]

It depends on what you're driving?

If it's a very low impedance load, <600R then use an audio amplifier IC, LM386, TDA2003 etc. for the output stage.