When I was in college we discussed op-amp circuits with a gain of less than 1, soooo......

Which means?

The circuit may have a voltage gain of less than one, but it can still have power gain depending upon the output load.

 

When I was in college we discussed op-amp circuits with a gain of less than 1, soooo......

sooo..... what?

 

sooo..... what?

So it proves (to him) that a circuit with a gain of less than 1 can be called an amplifier. But even that is not true, because the opamp is still amplifying the signal from its input to its output.

 

would it be possible to amplify a signal with this resistor circuit?


i put 'signal in/out' because i mean, if any works.

the theory question is basically, this circuit would present a voltage divider, so if a signal comes in at v2/v1, would this voltage result in a change in the voltage at v1/v2 , and in this configuration (or an alternate resistor organization) would it be possible to result in an amplification of the signal?

So @tsmspace
Been a while since your initial post,

You use the word "amplify" , which as you have seen is a little ambigious
Amplify could mean that Vout is >Vin , or it could mean Vout = Vin or Vout > Vin
Same for the current,

Hence comments , a transformer by this deifinition can increease a voltage , but at the expence of lowering the currnet available

Or that a op amp can output a lower voltage than the input voltage

Assuming you want to "amplify" the power in , then you need an active circuit , to get larger power out.

Just shifting the DC offset is not amplifying,
Your original circuit is AC coupled, so no DC offset there,

 

Yes, it is possible to use a transformer to increase the amplitude of a signal. But one must define the frequency(s) of the signal in question.

NO!! It IS NOT POSSIBLE to "amplify" a signal with a transformer, BECAUSE that does not increase THE POWER of the signal. AND, "AMPLIFY" means to increase THE POWER LEVEL of a signal. Either the voltage or the current can be adjusted, but not ampllified.

At this point it is rather important to look once again at the CORRECT MEANING of the word "amplify", and to actually understand what that means.

Literary "License" does not apply to technical meanings! And just because somebody makes some claim does not make it true! WE need to be aware of that!!
Certainly the gullible technical illiterate folks can be mislead, THAT has been shown throughout history! AND CERTAINLY there are those speakers who can present confusion as fact! Fortunately that has no effect on reality.
AMPLIFICATION still means to increase the power level of a signal, and physics shows that requires the addition of power from an external source.

 

In post #1 the TS presents this as the basis of his question.

The question is "Can you amplify a signal using only resistors?" The answer is no.

The term "Amplify" seems to have differing meanings from AAC member to AAC member. To me "Amplify" means to increase its power. Without adding power to the signal there can be no true amplification of the signal. Sure, you can use a transformer to increase the amplitude (voltage) but that comes at the cost of amperage. 10V @ 10A = 100W. If you increase the voltage to 20V the amperage drops to 5A. Either way you get 100W of power (again, assuming a perfect world). Static electricity may go as high as 50,000V static. But its current is so low that when you grab a doorknob or touch something that is at a much lower static voltage you get that darned annoying snap. But it doesn't kill you. Imagine 50KVs at 600mA. That's 30KW of power. At that kind of power you'd vaporize part(s) of your body and likely end up a former member of AAC. 50KVs at just 6mA is still 300W. If you survive that you'll have a heck of a burn.

Using the scheme the TS has posed it's not possible to amplify the signal. You CAN "Shift" the DC offset but you still don't get amplitude. I've been following this thread but for sure there's a lot of stuff I don't know or understand. If you can prove the increase of power using the circuit above then I'll stand corrected. Till then I'm with the "Nay" sayers.

 

And I don't consider transformers as "Passive" components.

 

Final thought from Jojo: If it were possible to amplify (increase the power) a signal just using resistors then we'd have true Over-Unity. "One" at best is equal to "One". Not "1.000001" and certainly not "2". Imagine if you could turn 1 into 2 with just resistors. I'd have free energy galore.
That's it from me.

 

And I don't consider transformers as "Passive" components.

Then you are in the minority.

 

Ahhh!

Then you are in the minority.

Transforming 120VAC to 1KVAC (as in a microwave oven) is anything but passive. A device that resists the flow of electrons is a passive device. In a circuit where 1 amp is available at any given voltage - a capacitor can only draw 1 amp of current until it charges. And as it charges the draw of amps diminishes. The ONLY circuit I can imagine that can increase the voltage in a passive manor is a voltage multiplier (using caps and diodes). That requires an alternating current to accomplish the feat. So running a circuit from a battery still requires active components to change the direction of the current.

I may be in the minority but that's not necessarily a bad thing. A majority of people may consider Hitler to have been a great leader. In that case being of the minority that doesn't consider him to have been a great leader seems rather satisfying to me.

Then again, there's a minority of people who believe the world is flat. In that case I'm of the majority. So either way - I still stand by my statements. If I AM of the minority - then it should be easy for someone as educated and experienced in these matters to show me a circuit that DOES amplify the signal. Can you do that?

 

the opamp is still amplifying the signal from its input to its output.

Where you stated that an op-amp that is outputting a lower signal than the original input, in this case I would not call this an amplifier, I'd call it an "Attenuator".

 

A simple lever is an amplifier.

 

Transforming 120VAC to 1KVAC (as in a microwave oven) is anything but passive.

But the transformer is passive in that process.

show me a circuit that DOES amplify the signal. Can you do that?

What does that mean?
Have you never seen a circuit that DOES amplify a signal (increase its power)?

 

A simple lever is an amplifier.

View attachment 367581

Use resistors now.

What does that mean?

What I should have said was "Show me a circuit using only resistors that amplifies an electronic signal".

 

Or a passive mechanical device that uses friction to “amplify” a force.

lever : transformer
resistor : friction

 

Use resistors now.

What I should have said was "Show me a circuit using only resistors that amplifies an electronic signal".

My point is, amplification is not restricted to power only.
Amplification can be applied to:

1. force
2. pressure
3. intensity
4. power
5. voltage
6. current

 

AAC: All About Circuits. i.e. power, voltage, current.
How would you amplify power without using any active components?
How would you amplify voltage without using any active components?
How would you amplify current without using any active components?

You can amplify speed using the gravitational pull of the sun and/or the planets. But we're not discussing that. The discussion is "Can you amplify a signal using only resistors?" Instead of amplifying the lift of a wing by adding air speed let's stick to the subject. "Can you amplify a signal using only resistors?" I'd like someone to show me how it can be done USING ONLY RESISTORS.

And I thought I was done with this thread.

 

Amplification of voltage using a transformer means a reduction in current. Power remains the same.
Amplification of current using a transformer means a reduction in voltage. Power remains the same.
Amplification of POWER means using some sort of voltage or current adder - hence an active circuit.

 

By JoJo's definition a resistor would be an active component because it actively converts electrical energy into thermal energy.

 

Also, one problem that can be pointed about the image in the OP is the poster said "only using resistors" but the image shows a separate energy source. (VCC)