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US 5,633,611 AGranted
Complementary current source circuit
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsHiroyuki Kohno, Takahiro Miki
Life of this patent
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Abstract
Driving circuits (6) output driving signals to drive switching transistors (Q 15, Q16). A potential as the high level of the driving signal can be set lower than a power supply voltage (V.sub.DD) by connecting the sources of transistors (Q18, Q20) to a node (X). This configuration prevents an overshoot at a switching time and allows an improvement in a settling time. Therefore, a complementary current source circuit for a high-speed D/A converter can be provided.
Claims6
A complementary current source circuit, comprising:
- a current source comprising
- at least one first transistor of a first conductivity type, having a first current electrode connected to a first power supply, a second current electrode and a gate to which a constant bias voltage is applied,
- a first switching transistor having a first current electrode connected to said second current electrode of said first transistor and a second current electrode connected to a first current output terminal, controlled by a first driving signal which is generated in accordance with a first digital signal, and
- a second switching transistor having a first current electrode connected to said second current electrode of said first transistor and a second current electrode connected to a second current output terminal, controlled by a second driving signal which is generated in accordance with a second digital signal;
- a first driving circuit for generating said first driving signal to drive said first switching transistor;
- and
- a second driving circuit for generating said second driving signal to drive said second switching transistor, wherein
- a first potential as the high level of said first driving signal is lower than a potential of said first power supply if the first conductivity type is P type, and
- a second potential as the low level of said first driving signal is higher than a ground potential if the first conductivity type is N type, wherein
- said first driving circuit includes a first inverter circuit and said second driving circuit includes a second inverter circuit,
- said first inverter circuit comprises a second transistor of the first conductivity type, having a source connected to said second current electrode of said first transistor, a drain for outputting said first driving signal and a gate, and
- said second inverter circuit comprises a third transistor of the first conductivity type, having a source connected to said second current electrode of said first transistor, a drain for outputting said second driving signal and a gate.
9 more elements
A complementary current source circuit, comprising:
- a current source comprising
- at least one first transistor of a first conductivity type, having a first current electrode connected to a first power supply, a second current electrode and a gate to which a constant bias voltage is applied,
- a first switching transistor having a first current electrode connected to said second current electrode of said first transistor and a second current electrode connected to a first current output terminal, controlled by a first driving signal which is generated in accordance with a first digital signal, and
- a second switching transistor having a first current electrode connected to said second current electrode of said first transistor and a second current electrode connected to a second current output terminal, controlled by a second driving signal which is generated in accordance with a second digital signal;
- a first driving circuit for generating said first driving signal to drive said first switching transistor;
- and
- a second driving circuit for generating said second driving signal to drive said second switching transistor, wherein
- a first potential as the high level of said first driving signal is lower than a potential of said first power supply if the first conductivity type is P type, and
- a second potential as the low level of said first driving signal is higher than a ground potential if the first conductivity type is N type,
- said complementary current source circuit further comprising:
- a voltage generator circuit comprising
- a second transistor of the first conductivity type of the same characteristics as said first transistor, having a first current electrode connected to said first power supply, a second current electrode and a gate to which said constant bias voltage is applied, and
- a third transistor of the first conductivity type, having a first current electrode connected to said second current electrode of said second transistor, a second current electrode connected to a second power supply and a gate connected to said second power supply so that said third transistor may be always conducted;
- wherein
- said first driving circuit includes a first inverter circuit and said second driving circuit includes a second inverter circuit,
- said first inverter circuit comprises a fourth transistor of the first conductivity type, having a source connected to said second current electrode of said second transistor, a drain for outputting said first driving signal and a gate, and
- said second inverter circuit comprises a fifth transistor of the first conductivity type, having a source connected to said second current electrode of said second transistor, a drain for outputting said second driving signal and a gate.
14 more elements
Dependencies are inferred from the claim text.