5.3

Input offset voltage drift overtemperature

The maximum input voltage drift variation overtemperature is defined as the offset variation related to the 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 overtemperature enables

the system designer to anticipate the effect of temperature variations.

The maximum input voltage drift overtemperature is computed using Eq. (1).

ΔVIOΔT=max VioT−Vio25°C

T−25°C

(1)

Where T = -40 °C and 150 °C

The TSU111H datasheet maximum values are guaranteed by measurements on a representative sample size

ensuring a Cpk (process capability index) greater than 1.3.

5.4

Using the TSU111H with sensors

The TSU111H has MOS inputs, thus input bias currents can be guaranteed down to 10 pA maximum at ambient

temperature. This is an important parameter when the operational amplifier is used in combination with high

impedance sensors.

The TSU111H is perfectly suited for trans-impedance configuration. This configuration allows a current to be

converted into a voltage value with a gain set by the user. It is an ideal choice for portable electrochemical gas

sensing or photo/UV sensing applications. The TSU111H, using trans-impedance configuration, is able to provide

a voltage value based on the physical parameter sensed by the sensor.

5.5

Fast desaturation

When the TSU111H goes into saturation mode, it takes a short period of time to recover, typically 500 µs. When

recovering after saturation, the TSU111H does not exhibit any voltage peaks that could generate issues (such as

false alarms) in the application (see Figure 20).

We can observe that this circuit still exhibits good gain even close to the rails, that is, Avd greater than 100 dB

for VCC = 3.3 V with Vout varying from 200 mV up to a supply voltage minus 200 mV. With a trans-impedance

schematic, a voltage reference can be used to keep the signal away from the supply rails.

5.6

Using the TSU111H in comparator mode

The TSU111H can be used as a comparator. In this case, the output stage of the device always operates in

saturation mode. In addition, Figure 5, Figure 6, Figure 7, show that the current consumption is not higher and

even decreases smoothly close to the rails. The TSU111H is obviously an operational amplifier and is therefore

optimized for use in linear mode. We recommend using the TS88 series of nanopower comparators if the primary

function is to perform a signal comparison only.

TSU111H

Input offset voltage drift overtemperature

DS14162 - Rev 1

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