LOW voltage amplification?

So you need a gain of 5/.02 = 250. That's a lot - you will have to be careful of noise, offsets, etc. If you want to get away from opamps, I'd try an instrumentation amp. The AD524 comes to mind, but I'm sure there are others out there. These typically have differential inputs and a good common mode rejection, and you can set the gain with a single resistor. Another possibility would be a current shunt amplifier. TI makes several - the INA193 is one I'm familiar with. You can search for it on the TI website. These are specifically designed to amplify voltages in the 20-100mV range to the 5V range.

You might consider an opamp / low pass filter circuit, if noise or instability is a problem. 60 Hz is almost DC, in opamp terms. Also, be sure if you are AC coupling the signal that you're using a large enough capacitor - capacitor impedance is inversely proportional to frequency.

Good luck!

A voltage gain transfer function of A_v=250 is not much. The nearly obsoleted OP27 has a minimum large signal gain of like 700 V/mV. A transimpedace amplifier, current shunt, will easily work at these values but will quickly drive a newbie nuts with it's possibly critical circuit layout requirements to prevent high frequency oscillations. Noise and offsets can be a nuisance depending on signal to noise and offset requirements.

But I guess after amplifying micro-volt signals in the middle of an electromagnetic storm of a particle beam lab, I forget how tricky this may seem to others.

You can use amplifier chips a very well known one is the LM380.

GA, But this illustrates the nature of electronics.
It's easy.... in theory.
In practice people have trouble even getting the power supply right, then they find the whole thing oscillating due to the high gain, poor layout etc.
My advice is to start with a lower gain first and work up to your final circuit, and if you don't have an oscilloscope, give up (You'd be surprised how many people try to build stuff without a 'scope)

(Single rail op amps are available and seem simpler at first glance), but then you need to worry more about DC conditions and/or AC coupling.

Del

Amen.

lighthash

You have to tell one more parameter and that is impedance of the signal source. 20mV as such is a very strong signal if impedance of the source is <1M Ohms. If impedance is few ohms then simply use step up transformer.

Whats your available supply voltage? You cannot effectively create 5VAC from 20mVAC. Need more parameters for a more detailed answer.

GA, we need to know exactly what he wants to do....and why!

Andy Germany,

Yes, user must tell exactly what is required or purpose of such voltage amplification.

Only voltage amplification is specified and that is for 60Hz signal which simply needs step up transformer with ratio up by X250. However if source current capability or impedance of the source was also specified then method of amplification to be used likely to change. It is not clear if it is a voltage amplification or also power amplification along with voltage amplification.

There is no further explanation possible.

Amplification is the control of a small force influencing a large force. You must have some kind of signal (influence) that controls a larger force (voltage, amps,etc). When I was very young I read an article on fluid amplification that made it very simple to understand. You can only control a larger force not generate it.

Check fluid amplification of google, bing or other search engine.

Hello,

Any opamp can do this. A text book opamp amplifier with a gain of 250 will do the job.How ever you have not mentioned weather yuor i/p is 20mV RMS or peak to peak.Presuming that it is p to p you will need minimum 9-0-9 power supply for opamp.

Note: P to P is 1.4 X Vrms

D M Daga

Basically i dont think what i want is possible, its just something that it got in my mind. i need to amplify a guitar amplifier signal to power up a stompbox (effects unit) to get rid of the 9v battery, so basicly is 20mv (i think) to 9v. (the stompbox connects in the middle of guitar and guitar amp)

thank you guys

Shame you didn't say this at trick one

Lightash, any coil pick-up electric guitar (assumption) will not generate enough power from the strings for your purpose.

Ok lighthash. Now that I know that you wish to amplify a guitar signal, an op amp circuit can be fabricated. However, as others here have pointed out you cannot do this without some additional power source. Your guitar pickups cannot power an effects box.

Let me change the topic slightly though and ask this. Why do you want to get rid of the 9V battery? If you tell us that, maybe I can help solve the actual root of your problem. (I do have an idea but before I say anything I need to know this.)

Does this project have anything to do with your first question? Please try to ask more serious questions giving enough detail to avoid wasting our time.Thanks.

If you play your guitar on a bicycle having a dynamo and then put the bicycle on a stand and enjoy doing this exercise along with music, then you can sure power it also. It will also get rid of your fat, improve your heart and lungs, strengthen your muscles. Call it body-o-music theme.

Why not feed the signal to an audio amp? That amplifies much weaker signals to power high wattage speakers and has a frequency range that includes 60Hz?

if i can get rid the battery then i can make a new series of effect units, planted on the guitars (e.x. chorus)

thank you

The only effect units you can do without power are the collection of passive audio modifications. This includes tone controls (high, low and band pass filters), volume, mixing of pickups. The cascade of briefly stored analog signals required to produce a chorus requires additional power. What some of the better pedal box companies use to do to prevent fading out during a song was having the power "ON" light fade out a good 15 minutes before complete lack of function. You might consider exploring this idea. But unless your pick up cable provides power you're out of luck.

you mean that all the power is coming out of the pickups and goes into the guitar amplifier and gets amplified?all this time i thought that it was the guitar amplifier that sends the power in the pickup and then back in and gets amplified.. if this is happening then the guitar is functioning with a magnetic field right?

Yes, That is correct, all my old electric guitars work that way i.e a permanent magnet, coil and of course a steel string. This signal is the amplified to the desired level. There are some new variants nowdays.