AC and DC voltage and current amplifying

[low5545]

I know that using bridge rectifiers ( http://www.cytron.com.my/viewProduct.php?pcode=DI-BR106&name=Bridge%20Rectifier%20BR106%20(10A600V) ) can convert AC voltage to DC voltage. Is it the same in AC-DC adapters? And using darlington transistor pairs can amplify the current of a voltage without any outside voltage help. (using transistors, not like op-amp) But is there an alternative component/circuit that does the same thing? And what component/circuit can be used to convert DC voltage back to AC voltage? Also what does a transfomer ( http://www.cytron.com.my/viewProduct.php?pcode=TF-6-0.5&name=Transformer%206V-0-6V%200.5A ) do?

[ABSF]

I know that using bridge rectifiers ( http://www.cytron.com.my/viewProduct.php?pcode=DI-BR106&name=Bridge%20Rectifier%20BR106%20(10A600V) ) can convert AC voltage to DC voltage. Is it the same in AC-DC adapters? And using darlington transistor pairs can amplify the current of a voltage without any outside voltage help. (using transistors, not like op-amp) But is there an alternative component/circuit that does the same thing? And what component/circuit can be used to convert DC voltage back to AC voltage? Also what does a transfomer ( http://www.cytron.com.my/viewProduct.php?pcode=TF-6-0.5&name=Transformer%206V-0-6V%200.5A ) do?

The questions that you asked are very basic electronics. Actually all the answers can be found in the book called "Art of Electrobics" by Winfield Hill and Horowitz. Try to grab a copy from your library and enjoy reading it.

A bridge rectifier can convert AC to DC pulses. After decoupling with electrolytic capacitors, it becomes DC.

Darlington transistors are not much different from ordinary transistors except they have very high gain. I dont know what you meant by "without any outside voltage help"? Can you give a simple circuit to illustrate your idea?

The circuit that converts DC back to AC is called an "Inverter".

Allen

[yonghui]

And using darlington transistor pairs can amplify the current of a voltage without any outside voltage help. (using transistors, not like op-amp) But is there an alternative component/circuit that does the same thing?

darlington pair, from what i know, is for small signal gain. its used for higher gain than a single transistor. i dont know that it is for amplifying current.
amplifier biased for current high current load normally does not does not provide high voltage gain, its just from driving low impedance load.
small swinging signal passing through darlington pair can give a higher output voltage swing. the purpose shud be almost the same as op amp. and op amp i think will do better job, since it can has differential pair input to supress the noise.
correct me if im wrong.


thanks&regards,
yh

[low5545]

If I want to amplify a 5V 40mA on a op-amp that is powered with the same voltage and current, will I get voltage and current gain?As I know, I can't get voltage/current higher than the power source. And that is what I mean. I want to amplify a current & voltage higher than my power source. Any suggestions? And what is the use of a transformer?

[yonghui]

the law of conservation of power applies. input power and output power should be same ideally, but due to losses, output power normally less than input power. amplifying signal means amplifying the input signal to a higher voltage,current, this lead to higher power of output signal compared to original input signal but this output signal is bounded to the power given to the amplifier, the output signal's wont be higher than what power source u give to the amplifier.

mayb u wan to generate energy?

[yonghui]

CODE: SELECT_ALL_CODE

If I want to amplify a 5V 40mA on a op-amp that is powered with the same voltage and current,

opamp is not for generating power. its for amplifying small signal.

for example a 10microvolt peak to peak sinusoidal signal, and ur opamp has the single voltage source +5V.

u can amplify the signal(10uV) to a output signal of sinusoidal, maximum will be less than 5V peak to peak.

mayb u r confused. amplifier ( opamp, transistor ) is not for boosting DC power to get more powerful source. but its for amplifying small signal. DC in small signal means no signal . small signal is variation of voltage on a DC level with respect to time. for example signal from microphone is small signal the variation of the voltage will be according to the voice.