TLC2652, TLC2652A, TLC2652Y

Advanced LinCMOS PRECISION CHOPPERSTABILIZED

OPERATIONAL AMPLIFIERS

SLOS019E − SEPTEMBER 1988 − REVISED FEBRUARY 2005

24

POST OFFICE BOX 655303

APPLICATION INFORMATION

theory of operation (continued)

During the amplifying phase, switch B is closed connecting the output of the nulling amplifier to a noninverting

input of the main amplifier. In this configuration, the input offset voltage of the main amplifier is nulled. Also,

nulled during the next nulling phase.

This continuous chopping process allows offset voltage nulling during variations in time and temperature over

the common-mode input voltage range and power supply range. In addition, because the low-frequency signal

path is through both the null and main amplifiers, extremely high gain is achieved.

The low-frequency noise of a chopper amplifier depends on the magnitude of the component noise prior to

chopping and the capability of the circuit to reduce this noise while chopping. The use of the Advanced LinCMOS

process, with its low-noise analog MOS transistors and patent-pending input stage design, significantly reduces

the input noise voltage.

The primary source of nonideal operation in chopper-stabilized amplifiers is error charge from the switches. As

charge imbalance accumulates on critical nodes, input offset voltage can increase, especially with increasing

chopping frequency. This problem has been significantly reduced in the TLC2652 by use of a patent-pending

compensation circuit and the Advanced LinCMOS process.

The TLC2652 incorporates a feed-forward design that ensures continuous frequency response. Essentially, the

gain magnitude of the nulling amplifier and compensation network crosses unity at the break frequency of the

main amplifier. As a result, the high-frequency response of the system is the same as the frequency response

of the main amplifier. This approach also ensures that the slewing characteristics remain the same during both

the nulling and amplifying phases.