AN4369

Internal resistances

DocID025335 Rev 1

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Internal resistances

Internally, the resistances are extremely well matched, meaning we can consider the ratios

of the actual values of R1, R2, and R3 over their respective targeted values to be identical.

Nevertheless, R1, R2, and R3 values vary from one TSC product to another due to process

variation and temperature.

The value of the resistance over temperature is defined by the following formula:

R(1 + TC*ΔT), where TC is the temperature coefficient and ΔT is T

If we take the temperature coefficient into account, we have:

As R3 and R1 are made of the same material, they have the same TC: G = R3/R1.

Therefore, the gain is related only to the ratio of R3 and R1. In other words, the gain is

independent of process variation and temperature. The final gain is well controlled and can

easily be trimmed during manufacturing.

R3

R1