Reference Voltage Circuit Temperature Compensation

The reference voltage generating circuit is divided into multiple independent transistor blocks (first through fourth transistor blocks) with distinct functions. Each block handles specific current paths and voltage generation tasks, allowing temperature compensation to be implemented as a separate functional module rather than mixing it with the basic voltage generation logic.

The circuit employs a composite structure combining depletion-type transistors (first and second transistor blocks) with enhancement-type transistors (third and fourth transistor blocks). This composite approach leverages the temperature characteristics of depletion-type devices (negative temperature coefficient) to compensate for the positive temperature coefficient of enhancement-type devices, achieving overall temperature stability.

The temperature compensation function is merged into the existing voltage generation structure by integrating the fourth transistor block (enhancement-type) with the third transistor block. The fourth block receives the reference voltage at its gate and generates a compensating current that flows through the bias voltage generating section, thereby embedding temperature compensation within the core voltage generation path rather than adding separate compensation circuitry.

The circuit utilizes parameter changes in transistor characteristics with temperature. Depletion-type transistors exhibit decreasing drain current with increasing temperature (negative temperature coefficient), while enhancement-type transistors show increasing drain current (positive temperature coefficient). By carefully sizing and configuring these transistors, the patent achieves parameter cancellation where the temperature-dependent parameters of different transistor blocks offset each other, maintaining stable reference voltage.

Each transistor block is designed with specific local characteristics tailored to its function. The first and second depletion-type blocks are configured for current generation with specific temperature coefficients, while the third and fourth enhancement-type blocks are sized to provide complementary temperature dependence. This localized optimization of transistor properties allows the overall circuit to achieve temperature stability without requiring extreme precision across all components.

The fourth transistor block receives the reference voltage at its gate terminal, creating a feedback mechanism where the generated reference voltage directly controls the compensation current. This feedback loop automatically adjusts the compensation level based on the actual reference voltage level, reducing sensitivity to manufacturing variations in transistor parameters and maintaining stability across process variations.