Reference voltage/current generation is essential to the Analog circuit design. There have been several ways to generate quality reference voltage using Bandgap Reference (BGR). There are mainly 2 types: Current mode and Voltage mode. The current mode bandgap reference (CBGR) is widely accepted in the industry due to the output voltage that is below 1V. However, its drawbacks include a lack of proportional to absolute temperature (PTAT) current availability, large silicon area, multiple operating points, and large temperature coefficient (TC). In this paper, various operating points are explained in detail with diagrams. Similar to the conventional voltage mode bandgap reference (VBGR) circuits, modifications of the existing circuits with only two operating points have also been proposed. Moreover, the proposed BGR occupies a much smaller area due to eliminating the Complimentary to Absolute temperature (CTAT) current-generating resistor. A new self-biased opamp was introduced to operate from a 1.05V supply, reducing systematic offset and TC of the BGR. The proposed solution has been implemented in 28nm CMOS TSMC technology, and extraction simulations were performed to prove the robustness of the proposed circuit. The targeted mean BGR output is 500 mV, and across the industrial temperature range (-40 to 125°C), the simulated TC is approximately 10.5 ppm/°C. The integrated output noise within the observable frequency band is 19.6 µV (rms). A 200-point Monte Carlo simulation displays a histogram with a 2.6 mV accuracy of 1.2% (+/- 3-sigma). The proposed BGR circuit consumes 32.8 µW of power from a 1.05 V supply in a Fast process, Hot (125°C) corner. It occupies a silicon area of 81 x 42 µm (including capacitors). This design can aim for biomedical and sensor applications.
Keywords: Bandgap reference; Noise; Operating points; Self-bias; Offset phase-margin
