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[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...
 

reidintransit

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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.
 

chuckey

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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
 

SanjKrish

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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..
 

reidintransit

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

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