5.1.2

Frequency domain

The frequency domain gives a more accurate vision of the chopper-stabilized amplifier architecture, especially

due to the chopping circuits it holds.

Figure 58. Input differential voltage

Figure 59. Chopped input diff. voltage

Figure 60. A1 amplification + intrinsic offset

Figure 61. Unchopped output diff. voltage + filter

When chopping the input signal, its frequency gets shifted around the switching frequency of the chop switches

(chopping frequency) and all its odd harmonics (frequency signature of a square signal). This enables the signal

to be frequency differentiated from the errors introduced by the first amplifying stage A1 (DC offset and flicker

noise).

After being amplified, the second chopper stage (Chop 2) demodulates the signal to its original frequency while

shifting low frequency errors around the chopping frequency.

These remaining spikes are then faded out by the notch filter, removing the errors introduced by the amplifying

stage.

5.2

ESD protection

Internal ESD diodes are present on every output and input pin of the TSB181, TSB182 ensuring a safe

conductive path in case of electrostatic discharge. Should the voltage on the pin exceed the power supply, its

ESD diode will become conductive and current will flow through it. This path is designed to resist ESD discharges,

however the input pins (IN1-, IN1+, IN2-, IN2+) are not rated to support a continuous (DC) current over 10 mA. In

such cases, a limiting resistor must be added to ensure that the input current absolute maximum rating (AMR) is

respected.

In addition, anti-parallel diodes have been added for protecting the safe operating area of the input MOS

transistors. These diodes shown on Figure 62 limit the differential input voltage to about 0.7 V. Hence, the input

current shares a relation with the differential input voltage: at any time, the differential input voltage should be

limited to 0.7 V or the input current to 10 mA, whichever comes first.

TSB181, TSB182

Application information

DS14357 - Rev 5

page 21/36