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alternating current amplification

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kattoju

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hi
i would like to know if its possible to amplify an alternatimg current from a signal generator. i need an amplified ac signal to drive a coil winding
 
im from a mechanical back ground..... so it would help me if yu were a little specific..anyways i came to know that op amps would only amplify an dc signal is it true?.. thank you.
 
No, an op amp will amplify either AC or DC, but may not have enough output current to power your coil.

And, as usual, we need more info. What is the frequency, voltage, and current the coil requires?
 
the frequency 15 hz- 1khz but i need to test it at 15 hz for sure. and voltage from the signal generator is 6.5 v .... the coil im using has a resistance of 400 ohm and the current through it is a 8.2 mA..... i would require more than a 30 mA....and the voltage amplified accordingly....
 
the frequency 15 hz- 1khz but i need to test it at 15 hz for sure. and voltage from the signal generator is 6.5 v .... the coil im using has a resistance of 400 ohm and the current through it is a 8.2 mA..... i would require more than a 30 mA....and the voltage may be a 30 v .....
 
Maybe something like this?

**broken link removed**

, replace the LS1 with ground. You can set the amplification with the resistors R9 / R10 ( not inverting amp) . You wont have crossover because the polarisation with the diodes. I think you can set your coil in the collector branch with a diode across .
 
what do yu mean by insert the coil in the collector branch?
i didn get that part ..... and y do i need two transistors?
 
You need 2 transistors to amplify the positive and negative side of the sinus. You just give a little bit information, I dont know what your purpose it. You can"t expect that we can just post the right schematic.
 
You need 2 transistors to amplify the positive and negative side of the sinus. You just give a little bit information, I dont know what your purpose it. You can"t expect that we can just post the right schematic.


hi,
im trying to build a test rig with an input coil and an out put coil.... both having resistance of a 50 ohm...a magnet is placed in the input coil ... when i energise the input coil the magnet moves out into the output coil there by inducing an emf in to it..... the problem im facing now is that when im using a signal generator ... i m only able to supply the input coil with 6 volts and its producing a current of 65 mA in the 50 ohm input coil. i need to supply the input coil vith more power and current ....
p.s: i need the voltage at low frequencies also for testing purposes. (10hz -20khz)
i want to amplify the power with out affecting the frequencies.....
 
Whats the supply Voltage? and with what type of circuitry did you manage to send 65mA trough the coil??
 
i used a function generator ..... which gave a sine wave of 7 volts pk-pk and the coil resistance was 50 ohm ... so i calcultaed the current across it... v=ir.... thats how i thought it worked isnt it?
 
Maybe something like this?

**broken link removed**

, replace the LS1 with ground. You can set the amplification with the resistors R9 / R10 ( not inverting amp) . You wont have crossover because the polarisation with the diodes. I think you can set your coil in the collector branch with a diode across .

hi sneakz,
can you tell me how to calcultae the current gain of the above circuit....
 
hi kattoju,
If the coil resistance is 400R and it conducts 8.2mA, means the voltage source is normally 3.28V

If you require to drive 30mA thru the 400R this would require a voltage source of only 12V, a 30V source would drive a current a current of 75mA thru the coil.

These figures do not include the coils inductance, which you have not defined.???
 
hi kattoju,
If the coil resistance is 400R and it conducts 8.2mA, means the voltage source is normally 3.28V

If you require to drive 30mA thru the 400R this would require a voltage source of only 12V, a 30V source would drive a current a current of 75mA thru the coil.

These figures do not include the coils inductance, which you have not defined.???

yu are right ... i havent taken the inductance in to consideration...... it is a 20 mH.... how do i calculate the current/ voltage now?
 
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