5

Application information

5.1

Operation theory

The TSZ18x is a high precision CMOS device. It can achieve a low offset drift and no 1/f noise thanks to its

chopper architecture. Chopper-stabilized amps constantly correct low-frequency errors across the inputs of the

amplifier.

Chopper-stabilized amplifiers can be explained with respect to:

•

Time domain

•

Frequency domain

5.1.1

Time domain

The basis of the chopper amplifier is realized in two steps. These steps are synchronized thanks to a clock

running at 2.4 MHz.

Vout

A1(f)

Filter

A2(f)

V

V

Chop 1

Chop 2

inp

inn

Vout

A1(f)

Filter

A2 (f)

V

V

Chop 1

Chop 2

inp

inn

the normal way.

Figure 47. Block diagram in the time domain (step 2) shows step 2, the second clock cycle, where Chop1 and

consequently divided by A1(f).

In the time domain, the offset part of the output signal before filtering is shown in Figure 48. Vio cancellation

principle.

TSZ181, TSZ182

Application information

DS11863 - Rev 5

page 17/43