When a temperature independent voltage reference is already available in an integrated circuit, temperature independent input switching thresholds are typically provided by a circuit configured as a differential transistor pair. One side of the differential transistor pair serves as the input, the other side is tied to the temperature independent voltage reference.
When a stable voltage reference is not already required for some other integrated circuit function, and supply voltage variations preclude using the supply voltage as a temperature stable voltage reference, the addition of a temperature stable voltage reference adds considerable cost to the integrated circuit. This added cost results from both the complexity of temperature independent voltage supplies and the silicon area required to integrate such reference voltage supplies into the circuit. One typical element of temperature stable voltage supplies is a feedback compensation capacitor. This element itself requires a large amount of additional silicon area on the integrated circuit, or may even be an external component.
USPTO Backgrounds
USPTO Backgrounds