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The effects of high and low input/output impedance

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watertreader

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Hi,

Would like to know what is the implication(advantage or disadvantage) of having high input impedance or low input impedance in a circuit.

What about high/low output impedance?

Thanks
 

Re: Impedance

Hi,

Input Impedance

Advantage

1) Low current taken from the circuit it is connected to.

Disadvantage

1) Is can pick up very low amplitude signals e.g. noise (hence filters have to be added increasing the circuit size).
 
Re: Impedance

Does this apply to high input impedance? Is there cases where low input impedance might be useful? Could we get more current with low input impedance?

Any good reference for this?

THanks
 

Re: Impedance

high input impedance means that you can recieve all the power
and low output impedance means that you can get all of the power to your load
 

Re: Impedance

I think low input impedence will be helpful for current-to-voltage amplifiers such as common-base circuit.
 

Impedance

Low input impedence allows one to apply a weak current signal without decrease in it's strenght.

High input impedence enables you to apply weak voltage signal without much change in it.
 

Impedance

we have low input current
 

Re: Impedance

Hi Dear watertreader!

Please, don't say Advantage/Disadvantage! Generaly speaking, it depends on the situation. I mean the Load and source which are connected to the circuit.
Suppose the Source behaves like a current source, then it's better to have a circuit with a low inpedance so that more current is drawn into the circuit in order to transmit maximum power.

However, if the source is like a voltage source, it is better to have a high input impedance.

The case of output is different. The impedance of load and the behaviour which we expect from the circuit defines the output impedance. For example if the circuit is going to be a current source connected to the load, well, it's better to have a low output impedance.

Thanks!
 
Re: Impedance

To get maximum power from a source u need to have a load impedance that is matched to the source internal impedance this is a power point of view.

To get maximum voltage from a source u need to have a very high i/p impedance.

To get maximum current from a source u need to have a very low i/p impedance.
 
Impedance

High i/p impedance means it takes less current from the source . and high o/p resistance means it gives high voltage at the o/p.
 

Re: Impedance

At Rf frequencies we don't want either high or low i/p or o/p impedance. It should be such that it will match with i/p 50 or 75 ohms.
 

Re: Impedance

@mansour
for example if the circuit is going to be a current source connected to the load, well, it's better to have a low output impedance.
Click to expand...

Is it not high output impedence for current amplifiers?
 

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