How to understand the curve graph of TL431?

灞波儿奔

How to understand the curve graph of TL431? [Copy link]

See the following graph in the 431 manual

How to understand this waveform? A small signal disturbance is generated at the REF terminal, and the output voltage changes accordingly?

Does it have anything to do with the voltage divider resistors 15K ohms and 8.25K ohms?

maychang

[How do you understand this waveform? A small signal disturbance is generated at the REF terminal, and the output voltage changes accordingly? ]

This is not a waveform. The so-called waveform must take time as the independent variable (the horizontal axis is the time axis). The vertical axis is voltage, current, power, pressure...

maychang

This curve shows the relationship between small signal voltage gain (logarithmic coordinates) and frequency (logarithmic coordinates). That is, [a small signal disturbance is generated at the REF terminal, and the output output corresponds to the change in output voltage].

maychang

[Is there any relationship with the voltage divider resistors 15K ohms and 8.25K ohms?]

The voltage divider resistors of 15K ohms and 8.25K ohms only determine the DC voltage at the REF terminal (about 2.5V), thereby determining the DC voltage at the Output terminal, so that the TL431 works in the middle of the linear state region.

Of course, these two resistors are connected to the circuit to form voltage negative feedback. The values of these two resistors will affect the depth of negative feedback, thereby affecting the curve. However, it only affects the height of the horizontal part of the curve (ordinate), and will not affect the overall shape of the curve.

吾妻思萌

This seems to be called an amplitude-frequency characteristic diagram? I don't know if that's what it's called.

吾妻思萌

I understand that any graph is a scattered point, and is sampled one by one against Nyquist.

Gen_X

The amplitude-frequency diagram mainly reflects the operating frequency range or bandwidth of the device.

From the figure, we can see that linearity can be basically guaranteed below 10kHz, but it can basically not be used above 1M.

The specific bandwidth has a theoretical definition, but you can evaluate the highest usage frequency yourself based on actual needs.

Sometimes, for price reasons, you have no choice but to sacrifice gain.

灞波儿奔

Gen_X published on 2023-3-1 19:29 The amplitude-frequency diagram mainly reflects the operating frequency range or bandwidth of the device. From the diagram, it can be seen that the linearity can be basically guaranteed below 10kHz, and it can basically not be used above 1M...

Thanks for your advice

After reading some information, I roughly understand that the amplitude-frequency diagram mainly reflects the operating frequency range or bandwidth of the device.

bmahu001

You can use Zhao Ke software to simulate it, which will help you understand it more deeply. This has a lot to do with practical applications and requires understanding.

This curve shows the relationship between small signal voltage gain (logarithmic coordinates) and frequency (logarithmic coordinates). That is, [a small signal disturbance is generated at the REF terminal, and the output output corresponds to the change in output voltage]

灞波儿奔

bmahu001 posted on 2023-3-7 13:37 nYou can use Zhao Ke software to simulate it, and you will understand it more deeply. This has a lot to do with practical applications and needs to be understood. ...

What simulation software do you recommend?

LTspice?

zgc135

This is equivalent to the relationship between the noise size under different frequency signals.