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Editor to share with you an example analysis of the input bias current in ios, I believe that most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

Input bias current Ib (Input Bias Current)

The input bias current is defined as the average bias current between the two inputs when the output DC voltage of the operational amplifier is 00:00.

The input bias current has a great influence on the places where the input impedance is required, such as high resistance signal amplification, integral circuit and so on. There is a certain relationship between the input bias current and the manufacturing process, in which the input bias current of the bipolar transistor is between ±10nA ~ 1 μ A; when using the field effect transistor as the input stage, the input bias current is generally lower than the 1nA.

For bipolar operational amplifiers, the discreteness of the value is very large, but it is hardly affected by temperature.

For MOS operational amplifier, the value is gate leakage current, which is very small, but is greatly affected by temperature.

The input bias current Ib is due to the leakage current in both input stages of the operational amplifier (as shown above).

And:

The input bias current defines the average of the two currents.

The input offset current is defined as the difference between two currents.

Source of input bias current:

Transistor: the base current of the transistor working linearly

FET: leakage current of input pin ESD protection diode (gate current of FET is very small)

Input offset current Ios (Input Offset Current)

The input offset current is defined as the difference between the two input bias currents when the output DC voltage of the operational amplifier is 00:00.

The input offset current also reflects the symmetry of the circuit inside the operational amplifier. The better the symmetry, the smaller the input offset current.

Input offset current is a very important index of operational amplifier, especially when precision operational amplifier or DC amplifier is used.

The input offset current is about 1% to 1/10 of the input bias current.

The input offset current has an important influence on small signal precision amplification or DC amplification, especially when a larger resistance is used outside the operational amplifier (for example, 10k or more). The influence of input offset current on accuracy may exceed that of input offset voltage. The smaller the input offset current is, the smaller the offset of the middle zero in DC amplification is, and the easier it is to deal with. Therefore, it is a very important index for precision operational amplifier.

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