Methods of Compensation for the Temperature Dependence of the Reference Voltage Sources of Integrated Circuits

The basic principles of reference voltage source construction are considered in the article. Possible sources of error of the output reference voltage, advantages and disadvantages of the existing architectural solutions of the reference voltage sources are analyzed. An architectural solution for the construction of a reference voltage source with higher order nonlinearities compensation is proposed, which has a temperature independent output voltage and is capable of operating at a supply voltage equal to or below 1 V. This solution has the possibility of implementing in the standard CMOS technology. Recommendations for compensation for the error caused by the offset voltage of the operational amplifier are given.

In the modern world, integrated circuits (ICs) are the nucleus of virtually all electronic systems. When designing many ICs, one of the most important tasks is to generate accurate voltages for the entire circuit. The ICs that create these voltages are often referred to as the reference voltage sources. The reference voltage is a major component of both fully analog and digital circuits and even memory elements. There is a particular demand for low voltage power supplies as it is required for modern gadgets, mobile phones, laptops, cameras, etc. They should have low sensitivity to changes in power supply, possible deviations in the parameters of the manufacturing process and temperature.

The reference voltage sources in standard CMOS technology have high precision output voltage, but temperature dependence is a problem. Another problem of such circuits is the inability to operate with a supply voltage below 1 V. The reasons for this are two: the principle of their operation is based on a bandgap of silicon equal to 1.25 V, which already exceeds 1 V of power; the second reason is that low voltage sources of reference voltage contain an operational amplifier, which should also operate at low power. In this case, low voltage power supply generators have poorer accuracy rates than classical implementation. Therefore, improving the characteristics of reference voltage sources while being able to operate at a supply voltage close to or below 1 V is a problem and requires a compromise solution.

In the article was analyzed  generators that provides proportional to absolute temperature (PTAT) voltage at their outputs, generators that provides complementary to absolute temperature (CTAT) voltage at their outputs. The source of the high-order nonlinearity was analyzed.

The schematic of implementing reference voltage generators was proposed. The formulas for output voltage was derivated. The basic principles of operation of proposed schematic was described.  The voltage reference, which utilizes the temperature-dependent currents generated from the parasitic n-p-n and p-n-p bipolar junction transistor devices in the CMOS process, is presented.