TLC2652AC-8DR Datasheet, PDF (24/39 Pages) Texas Instruments – Advanced LinCMOS PRECISION CHOPPER-STABILIZED OPERATIONAL AMPLIFIERS

TLC2652, TLC2652A, TLC2652Y
Advanced LinCMOS PRECISION CHOPPERĆSTABILIZED
OPERATIONAL AMPLIFIERS
SLOS019E − SEPTEMBER 1988 − REVISED FEBRUARY 2005
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,
external capacitor C_XB stores the nulling potential to allow the offset voltage of the main amplifier to remain
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.
24
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265