DocID024568 Rev 4

19/31

TSX9291, TSX9292

Application information

31

Whenever possible, it is best to choose smaller feedback resistors. It is recommended to

use 1 kΩ gain and feedback resistance (Rf and Rg) when gain = -1 is necessary. In the

application, if a large value of Rf and Rg has to be used, a feedback capacitance can be

added in parallel with Rf, to reduce or eliminate the gain peaking. Additionally, Cf helps to

compensate the input capacitance and to increase stability.

Figure 38 shows how Cf reduces the gain peaking.

Figure 38. Close loop gain vs. frequency with capacitive compensation

4.5

Input offset voltage drift over temperature

The maximum input voltage drift over the temperature variation is defined as the offset

variation related to offset value measured at 25 °C. The operational amplifier is one of the

main circuits of the signal conditioning chain, and the amplifier input offset is a major

contributor to the chain accuracy. The signal chain accuracy at 25 °C can be compensated

during production at application level. The maximum input voltage drift over temperature

enables the system designer to anticipate the effect of temperature variations.

The maximum input voltage drift over temperature is computed using Equation 1.

Equation 1

with T = -40 °C and 125 °C.

The datasheet maximum value is guaranteed by a measurement on a representative

1k

10k

100k

1M

10M

-30

-20

-10

0

10

20

Cf=1.5pF

Cf=1pF

Vcc=16V

Vicm=Vcc/2

Gain=-1

Cl=20pF

Cf=0pF

Frequency (Hz)

ΔT

------------

max

()

–

T25

° C

–

---------------------------------------------------

=