Semiconductor integrated circuit
View Patent ↗A bias circuit generates a first voltage at a first node. A second current source generates, according to the first voltage, a power supply current to be supplied to an internal circuit including transistors. A correcting transistor in a correcting circuit supplies the first node with a correcting current generated according to a constant voltage. Because of this, the first voltage is adjusted according to the correcting current. Therefore, the operating speed of the internal circuit is prevented from changing, being dependent on the variation of the threshold voltage and temperature variation of a transistor. As a result, the yield can be improved, independently of the variation of the threshold voltage among semiconductor integrated circuit chips, which occurs in a fabrication process. Further, temperature dependency of the operating speed of the internal circuit can be reduced, which can improve the yield of the semiconductor integrated circuit.
1. A semiconductor integrated circuit comprising:
a bias circuit that has a first current source for generating a first current and a load circuit connected in series with the first current source, and that generates a first voltage at a first node that is a connecting node between the first current source and the load circuit;
a second current source that generates a power supply current in accordance with the first voltage;
an internal circuit that has a plurality of first transistors and is connected to said second current source in order to operate the first transistors; and
a correcting circuit that includes a correcting transistor receiving a constant voltage at a gate, and that generates, in accordance with the constant voltage, a correcting current at a second node electrically connected to a drain of the correcting transistor, the second node being electrically connected to the first node, wherein:
the drain of the correcting transistor is connected to each gate of a pair of second transistors forming a first current mirror circuit; and
a drain of one of the second transistors that is not connected to the correcting transistor is connected to the second node.
2. A semiconductor integrated circuit comprising:
a bias circuit that has a first current source for generating a first current and a load circuit connected in series with the first current source, and that generates a first voltage at a first node that is a connecting node between the first current source and the load circuit;
a second current source that generates a power supply current in accordance with the first voltage;
an internal circuit that has a plurality of first transistors and is connected to said second current source in order to operate the first transistors; and
a correcting circuit that includes a correcting transistor receiving a constant voltage at a gate, and that generates, in accordance with the constant voltage, a correcting current at a second node electrically connected to a drain of the correcting transistor, the second node being electrically connected to the first node, wherein:
said bias circuit has a reference voltage generator that has
a threshold voltage compensating function for a variation of a threshold voltage of each of the first transistors formed in said internal circuit, and
a temperature compensating function for a temperature variation;
said reference voltage generator generating a constant reference voltage independently of the temperature variation and the variation of the threshold voltage; and
said bias circuit generates the first voltage in accordance with the reference voltage.
3. The semiconductor integrated circuit according to claim 2 , wherein
the reference voltage generator is a band-gap reference.
4. The semiconductor integrated circuit according to claim 2 , wherein
the correcting transistor is an nMOS transistor.
5. The semiconductor integrated circuit according to claim 2 , wherein
the correcting transistor is a pMOS transistor.
6. The semiconductor integrated circuit according to claim 2 , wherein:
said first current source and said second current source have a third transistor and a fourth transistor respectively whose gates are connected to the first node; and
the third transistor and the fourth transistor constitute a second current mirror circuit.
7. The semiconductor integrated circuit according to claim 2 , wherein
a drain of the correcting transistor is directly connected to the second node.
8. The semiconductor integrated circuit according to claim 2 , wherein:
a drain of the correcting transistor is connected to each gate of a pair of fourth transistors constituting a second current mirror circuit; and
a drain of one of the fourth transistors that is not connected to the correcting transistor is connected to the second node.