Texas Instruments OPA388 Precision Opamps
TI's OPA388 family of precision op amps are the first zero-drift, zero-crossover, rail-to-rail opamps available. They deliver high precision and linearity across the entire input range, and they're targeted at test and measurement, medical and safety, and high-resolution data acquisition.
Zero drift is critical for small signal, high gain, precision applications, and TI’s topology also achieves the lowest 1/f noise for precision measurements at DC or low frequencies. The OPA388 has multiple stages, but the first stage has a set of switches that inverts the input on each half-cycle, and another set that corrects the signal polarity before the second stage. This effectively averages the offset error to zero at the first stage and maintains the correct polarity on the output. This self-correcting technique results in an offset of just ±0.25 µV and offset drift of 5 nV/°C.
Crossover occurs in typical opamps because of the differential transistor pairs on the input used to achieve rail-to-rail operation. When the signal crosses over from the PMOS to the NMOS, or vice versa, there is some distortion when both transistor pairs are conducting. The OPA388 family uses a single transistor pair and an internal charge pump that boosts the input voltage stage so that this single transistor pair can cover the entire input range. This eliminates that transition, so there is no crossover, but it still provides a rail-to-rail input.
The OPA388 family is available in single, dual, and quad channel devices with a 10 megahertz gain bandwidth, and inputs are filtered for EMI and RFI. For more information on the OPA388 zero-drift, zero-crossover opamps, visit Mouser.com.
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