Introduction of oscilloscope bandwidth

Everybody knows , Oscillograph is known as the eye of electronic engineer , Then bandwidth is the top priority of oscilloscope technical indicators , It is also the most expensive indicator of oscilloscope , So what is the bandwidth of oscilloscope ？

Speaking of the bandwidth of the oscilloscope , Generally, it refers to the analog bandwidth of the front-end amplifier of the oscilloscope , Of course, this is in the digital oscilloscope and analog oscilloscope are the same . And the amplifier is equivalent to the door of the oscilloscope , Its bandwidth determines what kind of signal the oscilloscope can let in .

So how do you get the bandwidth of the oscilloscope ？

We can

Think about it

individual 1V The sine signal of , We input this sinusoidal signal into the oscilloscope , As the frequency of this sinusoidal signal increases , The amplitude of sinusoidal signal measured by oscilloscope reaches 0.707V When , Let's put the frequency of the sine signal at this moment , Defined as the bandwidth of the oscilloscope , That's what we're talking about -3dB spot , Cut off frequency point （ The amplitude decreases to 70.7%, The power is the same as the original ）

At this time, a frequency response curve may be needed to explain the change of the measured value of the oscilloscope with the measured frequency

When we measure the signal , Don't get stuck in the bandwidth of the oscilloscope. Measure , Because before reaching the cut-off frequency of the oscilloscope , The signal we measured has deviated from the real signal amplitude .

Of course, the above tests are only for sinusoidal signals , There are still many statements about the measurement of oscilloscope , But the author is dull , The structure of writing is not clear , Let me give you some other measurement examples , Related topics about bandwidth , Later, it will be improved slowly .

1） The signal we normally measure is not a sine wave , This involves the concept of harmonics , It will have a great impact on the bandwidth selection of the oscilloscope

2） Some signal frequencies are very low , But the rise time is relatively fast , It also requires a high bandwidth measurement system to restore the measured signal completely （ Here we introduce the concept of measurement system , It refers to the measurement system composed of oscilloscope and oscilloscope probe , Talk about it later. ）

3） For the above frequency response curve , The manufacturers of various oscilloscopes will also differ , The main reason is that the smoothness of the curve before and after the frequency cut-off point is different .