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Data Converters
Published in Wai-Kai Chen, Analog and VLSI Circuits, 2018
Ideally, the voltage reference Vref is a constant temperature- and supply-independent voltage with a zero output resistance. The most common voltage reference source is a silicon bandgap voltage reference of about 1.2 V. Depending on the process used, the bandgap reference voltage has a temperature coefficient of typically 20–100 ppm/°C at room temperature when it is set to a voltage ranging from 1.2 to 1.3 V. To generate a different reference voltage other than 1.2 V, op-amps are often used to make inverting and noninverting amplifiers with trimmable feedback gains. Because the bandgap voltage for zero temperature coefficient is not clearly defined and process dependent, it is common to trim this voltage at a wafer level, and it is extremely difficult to achieve an absolute accuracy over a wide range of temperature. However, most DAC applications, except for precision instruments, do not require an absolute accuracy of the reference voltage, and the load-driving capability of the op-amp used in the voltage reference is of paramount interest.
Voltage and Current References
Published in John D. Cressler, H. Alan Mantooth, Extreme Environment Electronics, 2017
Originally proposed by Widlar [1], a bandgap voltage reference is designed to provide an output voltage that is referred to the bandgap energy of the background semiconductor. The BGR circuit, therefore, requires at least one component with a port voltage related to the bandgap energy. In Si-based transistors, the base–emitter voltage (VBE) is the bandgap-related component and it is expressed as () VBE(T)=VG0−[VG0−VBE(T0)]TT0−VT(η−θ)In(TT0)
Bias and Current Reference Circuits
Published in Tertulien Ndjountche, CMOS Analog Integrated Circuits, 2017
The bandgap voltage reference structure shown in Figure 4.19(a) is designed to exhibit an output voltage that is almost independent of the temperature. This is achieved by compensating for the curvature introduced by the nonlinear temperature dependence of bipolar transistor characteristics on the output voltage.
A Simple structure with low temperature drift bandgap voltage reference design
Published in International Journal of Electronics Letters, 2023
Xinsheng Wang, Xicong Wang, Shimin Fan
At the beginning of the development of reference, the core device for designing reference was Zener diode. The design principle is to adjust the current of Zener diode, with the current limiting resistor to counteract the change of power supply voltage. Due to the large operating voltage and current of this structure, the integration level is not good. In 1970s, Widlar proposed the concept of bandgap reference first (Widlar, 1971). By using the weighted sum of ΔVBE and VBE to counteract the positive and negative temperature coefficients, the bandgap voltage reference which is independent of temperature can be obtained. Two years later, Kuijk broke the constraints of Zener diode required by traditional bandgap and designed an accurate circuit structure of bandgap by using amplifiers and thin film resistors (Kuijk, 1973). Then, Brokaw proposed a circuit structure that could greatly increase the precision of output voltage by eliminating the error which was introduced by the base current of Bipolar Junction Transistor (BJT), in (Brokaw, 1974). In 1979, Tzanateas et al. introduced Metal Oxide Semiconductor (MOS) devices into the bandgap to design a low-power bandgap in the weak inversion region (Tzanateas et al., 1979). At the end of the 20th century, Lee et al. proposed a high-order compensation technology for the temperature coefficient based on the Bi-CMOS process, which could reduce the temperature drift of the bandgap voltage reference through the exponential curvature compensation technology. However, as the technology requires a high value of BJT, the application scope is limited (Lee et al., 1994). There are several curvature compensation techniques to reduce the temperature drift (Koudounas et al., 2010; Hu et al., 2010), such as high-order temperature compensation technologies. Some circuits use complex structures to get a high performance and low mismatch spread (Wadhwa & Chaudhry, 2017) bandgap voltage reference, but they use stack of MOSFET (Singh et al., 2018).