| 摘要 |
A thermostat circuit (FIG. 4) is provided which (i) works properly with very low supply voltages, (ii) does not need a separate constant value as a reference, and (iii) has improved temperature sensitivity over prior art thermostat circuits. The thermostat circuit compares two reference currents-IPTAT and IVBE. When IVBE>IPTAT, the output of the thermostat circuit is one logic state (either high or low). When IPTAT>IVBE, the output of the thermostat circuit is a different logic state (either low or high). Current IPTAT comes from a PTAT current generator (FIGS. 5-7), and current IVBE comes from a VBE current generator (FIGS. 8-10). The PTAT current generator and the VBE current generator may be implemented with cascode amplifiers. In an embodiment, the currents IPTAT and IVBE can be compared at a current comparator circuit (FIG. 11) with a summing node and an output node. The total current at the current comparator's output node is independent of temperature, and the output node exhibits a hysteresis behavior. The thermostat circuit can include a testing/tuning circuit (FIG. 12) which is capable of injecting a test current into or subtracting a test current out of the summing node.
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