input impedance, output impedance

[PG1995]

Hi

I roughly understand the term 'input impedance' which means very high input resistance and such an equipment would need very little input power to operate with. But what does the term 'output impedance' mean? Perhaps, it means that the equipment wastes very little power and most of the power generated by it is outputted. And when DMM is connected across output terminals of such a device, the DMM reads very little resistance as compared to when it's connected to input terminals. Please help me with it. Thank you.

 

[colin55]

Suppose we have a circuit that has a LOW OUTPUT IMPEDANCE.
This means it will deliver a high current to a load.
The output voltage may be 1v or 200v – we are only describing the current capability of the circuit.
The term LOW OUTPUT IMPEDANCE is relative and it may be VERY LOW when compared to one amplifier or medium output impedance when compared to another amplifier.
It also means the amplifier (or circuit) should be connected to a low impedance (resistance) device to allow the maximum transfer of current (energy).

 

[audioguru]

An opamp that has negative feedback and is not clipping has an extremely low output impedance but not a high output current.
It can drive a load of 2k ohms with an extremely low output voltage loss.

An audio amplifier that has negative feedback and is not clipping has an extremely low output impedance. It has a fairly high output current.
It casn drive a load of 4 ohms or 8 ohms with an extremely low output voltage loss.

 

[Ratchit]

PG1995,

I roughly understand the term 'input impedance' which means very high input resistance .....

You understand wrong. The input impedance is the change of voltage divided by the change of current at the input terminals.

But what does the term 'output impedance' mean?

The output impedance is the change of voltage divided by the change of current at the output terminals.

Perhaps, it means that the equipment wastes very little power and most of the power generated by it is outputted.

Why are you speculating? Those parameters are very well defined throughout the electronics field.

Are you aware than if you know the transfer function of a linear circuit, you can easily find the input and output impedances from the denominator of the equation?

Ratch