A chopping-free single-trim bandgap reference using amplifier with PTAT offset

This article presents a chopping-free single-trim bandgap reference with an amplifier proportional-to absolute temperature (PTAT) offset. This amplifier PTAT offset is helpful for improving the BGR accuracy. Unlike the classic differential amplifiers, whose input-referred offset is usually non-PTAT, the proposed amplifier realizes a PTAT offset through controlling the current of a BJT-based structure. Similar to other PTAT error sources in a bandgap reference, this PTAT offset can be eliminated easily through a single room-temperature trim at the reference voltage. This makes the proposed circuit very simple and highly accurate, since it eliminates the need of complicated amplifier-offset cancellation techniques, such as chopping or autozeroing, that are usually used in prior single-trim bandgap reference circuits. It also eliminates the high-frequency ripple at the reference output, due to the no need of chopping. Besides the proposed structure, this article also presents a new technique to generate the amplifier bias current using only a tail resistor. Since a complicated biasing circuit is no longer needed, the proposed circuit is further simplified. Implemented in a 180-nm BCD process, the temperature coefficient (TC) is 3–8 ppm/◦C at −55 ◦C∼125 ◦C after a single trim at the room temperature, the output noise is only 1.5 µVrms at 0.1–10 Hz, the current consumption is 590 µA, and the active area is 0.55 mm2. According to the best of our knowledge, this is the first ever single-trim bandgap reference with no need of chopping or autozeroing.

Subjects

Bandgap reference | proportional-to-absolute-temperature (PTAT) amplifier offset | single trim

DDC Class

600: Technology

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A chopping-free single-trim bandgap reference using amplifier with PTAT offset