So I'm playing with some experiments, there's this thing. Basically, as whatever signal generator thingy goes higher and higher frequency, the amplitude is less and less. To get a big strong signal, I can lower the frequency, but at higher frequency there's really no way to get a big strong signal.

Ok I understand some of what's going on here, but when I go to look up how to learn more about electronics, I'm basically not there in the learning curve, so what my question is, is what sorts of "topics" am I looking to learn more about? What are the words I would be using to search for explanations, what specific field of electronics discusses this in greater detail, what are some of the basic overall ideas to be aware of (like, some kinds of amplifiers are better able to make big strong high frequency signals, what are the common traits of these amplifiers).

I would like to understand some of the things I have been observing playing with some kits, like why it is that if I measure this particular "crystal tester kit" where I can see the crystals signal using the oscilloscope, the tester is no longer able to detect the frequency. I understand that the impedance of an amplifier has to be tuned to a bandwidth to see gain at that bandwidth, but don't know things like how wide these bandwidths are, if higher frequency amplifiers never see high gain and multiple stages are always required, or if the signal is ever able to be preserved so that measuring the input and output can actually show the same 'waveform fingerprint' (for example for me it is always clipped before or after and then not before or after, with clipping being just as frequently lost as it is gained).


Basically, I don't know how to search for this information.

 

You are asking people on the Internet to explain to you why some that is only defined as a "signal generator thingy" behaves a certain way and actually expect a meaningful response?

 

You are asking people on the Internet to explain to you why some that is only defined as a "signal generator thingy" behaves a certain way and actually expect a meaningful response?

XR2206 function generator circuit | ElecCircuit.com

DDS Signal Generator Kit DIY 1-65535HZ Digital Function Generator with Sine Triangle Square Saw Rotating Triangle Waves-A75P - AliExpress 13

ICL8038 Multi-Function Low-Frequency Signal Generator Multi-Wave Welding Electronic Circuit Experiment Kit DIY - AliExpress 502

things like these things

 

No, that is not correct. A well designed signal generator can keep its magnitude constant over a wde range of frequencies. You cannot generalize from your experience with a dirt cheap toy signal generator.

 

May I quote?
I understand that the impedance of an amplifier has to be tuned to a bandwidth to see gain at that bandwidth, but don't know things like how wide these bandwidths are, if higher frequency amplifiers never see high gain and multiple stages are always required, or if the signal is ever able to be preserved so that measuring the input and output can actually show the same 'waveform fingerprint' (for example for me it is always clipped before or after and then not before or after, with clipping being just as frequently lost as it is gained).

I must admit that I do not understand this part of your contribution.

 

It is a characteristic of all active devices that, due to the physics of electron movement and their construction, as frequency increases, gain decreases. This is gathered together for opamps and other active devices in the datasheet parameter 'gain-bandwidth', the frequency at which gain is effectively 1. So if you want, for example, an audio amplifier giving a gain of 50 at 20kHz you need an amp with a gain-bandwidth of at least 20 * 20kHz = 400kHz and preferably double that. That's for a sine wave. Of course if you are amplifying a square wave (not just switching) you need to include at least the 3rd and 5th harmonics of the fundamental frequency to preserve the 'shape'.

A closely related parameter for opamps is the slew rate in volts/Sec, or more commonly volts/uS. This is a measure of how fast the amplifier can change it's output voltage; clearly an amplifier with a high gain-bandwidth must have a high slew rate as well.

 

An amplifier "tuned to a bandwidth" is not how they are normally described.

Usually, an amplifier is designed to amplify some specific range of frequencies, such as "audio frequency", or either a range of radio frequencies, or, in many cases, a specific frequency. The "wideband" amplifier is possible but to actually be a broad-bandwidth amplifier, (beyond audio frequencies) requires a rather deliberate design effort.
Certainly, almost every amplifier is designed to amplify some particular frequency range of interest.
There are amplifiers designed to only amplify a very narrow band of frequencies, usually called "tuned amplifiers", and also those designed for wider bands of frequencies, called "untuned " amplifiers. The circuits are quite different.

 

So I'm playing with some experiments, there's this thing. Basically, as whatever signal generator thingy goes higher and higher frequency, the amplitude is less and less. To get a big strong signal, I can lower the frequency, but at higher frequency there's really no way to get a big strong signal.

Ok I understand some of what's going on here, but when I go to look up how to learn more about electronics, I'm basically not there in the learning curve, so what my question is, is what sorts of "topics" am I looking to learn more about? What are the words I would be using to search for explanations, what specific field of electronics discusses this in greater detail, what are some of the basic overall ideas to be aware of (like, some kinds of amplifiers are better able to make big strong high frequency signals, what are the common traits of these amplifiers).

I would like to understand some of the things I have been observing playing with some kits, like why it is that if I measure this particular "crystal tester kit" where I can see the crystals signal using the oscilloscope, the tester is no longer able to detect the frequency. I understand that the impedance of an amplifier has to be tuned to a bandwidth to see gain at that bandwidth, but don't know things like how wide these bandwidths are, if higher frequency amplifiers never see high gain and multiple stages are always required, or if the signal is ever able to be preserved so that measuring the input and output can actually show the same 'waveform fingerprint' (for example for me it is always clipped before or after and then not before or after, with clipping being just as frequently lost as it is gained).


Basically, I don't know how to search for this information.

I assume then, you have an oscilloscope to observe the drop in amplitude?

 

Hello,

If you got an oscilloscope, wich one do you have?
The bandwidth of the oscilloscope must be higher than the object you measure.

Bertus

 

Hello,

If you got an oscilloscope, wich one do you have?
The bandwidth of the oscilloscope must be higher than the object you measure.

Bertus

True indeed, good point !

 

I assume then, you have an oscilloscope to observe the drop in amplitude?

I have two, one of which the bandwidth is too small, so I know. it actually shows a signal too, but just shows them all as 1mhz when it picks one up, even though it's like 10mhz. I have the fnirsi dso153 , which is better because it can pick up signals as weak as 10mvpp , but is limited to about a 1mhz bandwidth , and i have the fnirsi 1014d which can't see below about 30mvpp, but is able to see higher frequency, based on videos I have watched probably it will be good to 40mhz, fine to 60mhz, and dodgy after that although rated at 100mhz.

 

I have two, one of which the bandwidth is too small, so I know. it actually shows a signal too, but just shows them all as 1mhz when it picks one up, even though it's like 10mhz. I have the fnirsi dso153 , which is better because it can pick up signals as weak as 10mvpp , but is limited to about a 1mhz bandwidth , and i have the fnirsi 1014d which can't see below about 30mvpp, but is able to see higher frequency, based on videos I have watched probably it will be good to 40mhz, fine to 60mhz, and dodgy after that although rated at 100mhz.

Electronics is a highly specialized branch of physics, it is science and details matter. Show us pictures of what you see on your scope at different frequencies, how does your oscillator actually generate its signal, does it rely on D/A ?

The XR2206 starts to drop amplitude after 200KHz, did you know that?

Also: https://www.eevblog.com/forum/dodgy-technology/dont-buy-any-kit-with-xr2206-wfg/

You may see a little bright red board WFG kit, in particular. DON'T BUY!!!

 

Consider that first, you have not mentioned the output of your signal generator, I don't think. OR, is it possible that you are comenting on the amplitude of your signal generator device itself??
REALLY!! The post #1 is not clear to me as to which signal you are commenting on.

What needs to be mentioned is that signal generator output varying with the frequency has been an issue with signal generators for as long as they have been around!! So the TS is not commenting on somethig new at all! It is at least as old as signal generators.

All of the comments so far have been correct, although possibly not easy to understand.
The very simplified physics explanation is that as the frequency rises, the motion speed of the electrical field moves faster, and faster motion always requires more energy. So if the greater energy is not provided, then the result is less electrical field movement, which directly equals a lower voltage.