[SOLVED] When to use voltage amplifier, current amp & a power amp

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SanjKrish

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Say I have an antenna or a microphone.. and I want to amplify the signal should I use a current amplifier or a voltage amplifier or a power amp and why??

Can a weak source like the antenna supply voltage or current.. I'm so confused on how voltage, current and power behaves..

Additional info.. Things which I know..
I read that for a voltage amplifier the input impedance should be high so as to tap all the voltage across the feeble input could provide..
for a power amp the input resistance should be equal to the resistance of our source say in our case the antenna
and a current amp will have very low resistance so that all the current flows across the input terminals of the amp...
 

If the antenna is used as a receiving antenna then you'll want a voltage amplifier with low noise (LNA) to prevent amplifying or introducing noise. The power amplifier is used on the output for a power supply or when you need high voltage and current and is usually preceded by a voltage amplifier.
 

For high frequency RF amps (Fc> 100 MHZ), the aerial is normally connected by a bit of Coaxial cable that matches the aerials impedance -in the range 50-75 ohms. In this case you still want a voltage amplifier, but if the device is matched to the low impedance, then extra gain or linearity can be got at no no expense, such as using a grounded base transistor.
Current amps are unusual, I have never seen one because if you need a high current output, then normally you need a reasonable voltage to drive the current into the load, so you have a power amplifier.
Frank
 

Thanks reidintransit & chuckey for ur explanatin...

Actually I dont have a very gud basic idea about were we would use a voltage source and current source.. so i was confused whether we shd do voltage amplification or current amplification or power amp...

reidintransit U gave me the idea that a voltage amp is needed to boost the signal strength but if we need to drive a huge load, in tat case the voltage amp would be preceded by a power amp..

n chuckey I got from u that we don't usually use current amp as all our output devices like speaker or anything are react to voltage across its input leads (like I should connect it to a 240V power supply etc) and not current and tat is the reason why we don't find current amps in common..
 

voltage amplifier followed by power amplifier not preceded by power amplifier. Generally want power amplifier at last stage of circuit.
 

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