Monolithic Voltage Reference Output Thermal Drift Sensitivity
Monolithic reference thermal drift sensitivity combines silicon junction non-linearities, piezoresistive mechanical package stress, and solder reflow hysteresis.
Ctat Voltage
Temperature Characteristic
An analog potential that decreases linearly as the ambient temperature rises. In semiconductor design, a ctat voltage relies on the base-emitter junction of a biased transistor. This relationship provides a predictable slope for thermal compensation.
Physical Origin
Bipolar junctions exhibit a temperature-dependent energy bandgap that dictates their conduction threshold. When biased with a constant current, the voltage drop across the junction narrows as thermal energy increases the intrinsic carrier concentration. This change forms the physical basis of the ctat voltage, making it an essential building block for bandgap reference circuits.
The resulting signal can be summed with a positive coefficient voltage to achieve temperature independence.
Calibration Method
Trimming stabilizes the absolute value of the voltage at a baseline temperature. Silicon processing variations can shift the base-emitter voltage by several millivolts, altering the start point of the temperature ramp. Multi-point trimming routines during wafer testing resolve these offsets, ensuring that the ctat voltage tracks the target curve across the full industrial temperature range.
System Integration
Variations in the bias current can distort the linearity of the thermal response. If the current source itself has a temperature coefficient, it injects a non-linear curvature into the ctat voltage curve, creating an error term. Designers minimize this effect by utilizing high-precision current mirrors that maintain a stable output regardless of local thermal fluctuations.
Achieving this isolation guarantees that the output voltage remains a true representation of the local silicon temperature.