A voltage reference using a temperature-dependent current to bias a junction diode
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Bandgap voltage-reference circuits generate an appropriate amount of a voltage that varies proportionately to absolute temperature (called PTAT), to cancel the complementary to absolute temperature voltage variation (known as CTAT) of a current biased p-n junction diode so that the sum of the two voltages remains constant with respect to temperature. The bandgap voltage of Silicon is approximately 1.1V. It is inconveniently large to generate and use in short-channel circuits where the supply voltage is limited 1.2V. So the idea presented here is to maintain a constant reference voltage of around half the supply voltage (700mV) across a junction diode. A simple circuit for generating the bias current with appropriate temperature dependence for biasing a diode is presented. Simulation results in 55 nanometer technology demonstrate the feasibility of this scheme. The performance that is achievable is a reference voltage with less than 1 percent variation in the temperature range of 0 to 100 degrees C.