SLOS161C - OCTOBER 1996 - REVISED OCTOBER 1997
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LinEPIC and Self-Cal are trademarks of Texas Instruments Incorporated.
The TLC4502 self-calibrating operational amplifier utilizes the recent availability of on-chip digital and analog signal processing to automatically null the input offset voltage at power-up. This self-calibrating feature requires typically 300 ms to complete and is repeatable to within ±3 uV on successive calibrations. The technique involves the extraction and digital storage of the key offset-nulling information. This information is retained without degradation as long as the circuit is powered. This eliminates the need for continuous chopping of the input signal to refresh the offset information. Once the process is complete, the bulk of the calibration circuitry drops out of the signal path and shuts down. This minimizes or eliminates any effect the calibration circuitry might have on the desired signal path. It also allows the TLC4502 to be used exactly like any other operational amplifier after the calibration cycle is complete.
The TLC4502 is a high-performance operational amplifier fabricated in a 1-um 5-V digital CMOS technology. It achieves very high dc gain, as well as excellent power supply rejection ratio (PSRR) and common-mode rejection ratio (CMRR). It uses a mixed-mode (analog/digital) internal compensation loop with digital storage of the offset information and a current-mode output to reduce its input offset to < 50 uV. The TLC4502 also features a rail-to-rail output structure capable of driving loads to 1 k and 1 nF. Unlike existing commercially available low-offset high-precision amplifiers, the TLC4502 needs only a single 5-V supply, requires no trimming, and uses no bipolar transistors or JFETs.
To achieve high dc gain, large bandwidth, high CMRR and PSRR, as well as good output drive capability, the TLC4502 is built around a 3-stage topology: two gain stages, one rail-to-rail, and a class-AB output stage. A nested Miller topology is used for frequency compensation
View more information about generic part numbers:TLC4502, TLC4502A, TLC4502M
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