can i apply ohm's law to alternating current & voltage ?

[sayf alawneh]

it may be a stupid question ,but if i dont ask it i'll stay stupid -_-
am still a beginner ,
any ways here are my questions:
am amplifying an AC signal using common emitter amplifier , that will amplify the input voltage and give me a higher out put voltage , will it also give me a higher output current ??
also,suppose that i wanna amplify 2 volts up till 15 volts and connect the output amplified voltage to a coil will that force a higher current than that current forced by the 2 volts to move through the coil ??
in other words can i apply ohm's law to alternating current & voltage ?

 

[barry]

Re: question for experts

will it also give me a higher output current ?? --It CAN. It will depend on your load resistor.

will that force a higher current than that current forced by the 2 volts to move through the coil ??--Of course. A transistor is actually a current amplifying device. The collector(load) current is a multiple of the base current. That's the "beta" or "hfe" of the device.

in other words can i apply ohm's law to alternating current & voltage ? -- Absolutely.

 

[D.A.(Tony)Stewart]

Re: question for experts

The impedance of a coil Z(L)= 2pi*f*L is your load... unless it is moving like a solenoid or speaker.

If the source impedance is much lower than the load coil, the signal attenuation should small and has the widest frequency response.

This is the advantage of Emitter Follower. Zout=Zin/hFE .. approx. it is now like a voltage source.
.
whereas the Common Emitter output impedance is the Collector Impedance from the transistor behaving as a current source.


If the source impedance is equal to load impedance, the voltage reduces 50% but current yields the most power to the load possible.

- impedance and voltage on the collector rises with rising frequency for a coil. So the current limit is dropping as well.



You can put the coil between collector and V+, keeping in mind you are conducting DC current and modulating it with AC + DC input. You only get voltage gain by raising the collector impedance, but you not have any gain if the coil impedance is too low. Voltage Gain is the ratio of collector to emitter impedance..

If the impedance is not high enough, a 2nd stage EF after CE may be necessary.

The CE , common emitter, will tradeoff output impedance with voltage gain.

 

[Audioguru]

Re: question for experts

What is your "coil"? If it is a loudspeaker then your common emitter transistor operates in class-A and gets hot even when not playing.
Since your transistor is not a real amplifier then it probably does not have any negative feedback so its distortion will be terrible.

 

[barry]

Re: question for experts

What is your "coil"? If it is a loudspeaker then your common emitter transistor operates in class-A and gets hot even when not playing.
Since your transistor is not a real amplifier then it probably does not have any negative feedback so its distortion will be terrible.

Just because there's no feedback, and just because there's distortion doesn't mean it's not a 'real' amplifier.

 

[Audioguru]

Re: question for experts

Just because there's no feedback, and just because there's distortion doesn't mean it's not a 'real' amplifier.

I forgot about horrible-sounding acid rock "music". It can amplify that stuff.

 

[barry]

Re: question for experts

But it's still an amplifier. And it's still music.