# voltage amplifier??

Discussion in 'The Projects Forum' started by rand, Feb 15, 2009.

1. ### rand Thread Starter Member

Jan 13, 2009
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0
I would like to know where how I could make a circuit to increase the voltage of my AC signal from a function generator... the generator itself doesn't really have its own amplifier (too low)...

i have a 2N3055 NPN Transistor
and another pnp one from radioshack

i guess i need a common base amplifier.., but i have no idea how to calculate resistors or capacitors if u need them?

2. ### SgtWookie Expert

Jul 17, 2007
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How much voltage does the function generator currently output, and through what frequency range?

What kind of current output are you expecting?

3. ### rand Thread Starter Member

Jan 13, 2009
14
0
well if u measure voltage of the generator just by putting the leads to the generator its only a .2v - but thats nothing right? i directly hook it up to an led and its 2.1V
i thnk the voltage is 3vp-p and the range of frequency is from 0-5mhz

frequency is probably > 1 mhz depending on setup but im using about 1.68mhz right now

basically i want to increase the distance the coils can be in our setup so the led still lights up... so a higher voltage should allow that?

function generator-> coil with capacitor
another coil gets energy from magnetic field of other coil - to capacitor + led

Jul 17, 2007
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5. ### rand Thread Starter Member

Jan 13, 2009
14
0
yea i might try it again with only the second section of it without using the op-amp because it kinda just messed up... increased amps didn't help the distance?

6. ### Audioguru New Member

Dec 20, 2007
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The opamp increased the voltage swing and the transistors increased the current. the increased voltage and current results in increased power to the coil you are driving. But the opamp has a max frequency of 100kHz, not 5MHz.

The coil is an inductor. It uses less current and less power as the frequency is increased. But it can be tuned to the frequency you are using then it will be much more powerful if the generator's amplifier can provide it with plenty of power.

7. ### rand Thread Starter Member

Jan 13, 2009
14
0
yea making the coil tuned to the frequency is kinda the problem then - i dont have an inductance meter - i have a multimeter and capacitors and resistors.. so i have no idea how to calculate the inductance of the coils

8. ### rand Thread Starter Member

Jan 13, 2009
14
0
o so if the max frequency is 100 khz - i just have to tune the coil to 100khz somehow

Jul 17, 2007
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