A low noise CMOS operational amplifier in a 1.2 mu m digital technology

A low noise CMOS operational amplifier has been fabricated in a standard 1.2- mu m digital technology. The op amp has a 3.0-mm/sup 2/ area. The layout and fabrication are described. The design requirements of the op amp included low power consumption, low input offset voltage, a gain-bandwidth product of at least 250 kHz, a 1/f noise corner of 100 Hz or lower, a midband equivalent input noise voltage of 10 nV/ square root Hz or less, and operation at +or-2.5 V. The primary design requirement of the low frequency amplifier (LFA) was the minimization of the equivalent input noise of the op amp, especially the 1/f noise at frequencies between 100 Hz and 10 kHz. One useful means of evaluating the performance of the LFA is to compare the op amp's characteristics to the typical parameters of the Texas Instruments TLC2201. This comparison indicates that the LFA's performance is approximately equal to that of the TLC2201 in most respects.<
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