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US 2003/0197552 A1Published application
Reference voltage source circuit operating with low voltage
AssigneeRicoh Company, Ltd.
InventorHirofumi Watanabe
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AssigneeRicoh Company, Ltd.
InventorHirofumi Watanabe
Estimating the term…
A reference voltage source circuit, which can generate a sufficiently low reference voltage and which can stably operate at temperatures above 80 degrees Celsius, is provided. The circuit comprises two MOS transistors with gates of equal temperature characteristics of threshold voltage but of different impurity concentrations. The difference of voltages between the gates and the sources of the two MOS transistors is obtained as the reference voltage. When the gates of two transistors are connected together, the source of one of the transistors is connected to the ground, the difference of voltage between the gate and the source of two transistors becomes the source voltage of the other one of the transistors, and this source voltage of the other one of the transistors becomes the reference voltage.
A reference voltage source circuit comprising:
A reference voltage source circuit comprising:
A reference voltage source circuit comprising:
Dependencies are inferred from the claim text.
From the US filing history. Foreign family members aren’t listed.
Backward citations are indexed for grants only.
With compensation for device parameters, e.g. channel width modulation, threshold voltage, processing, or external variations, e.g. temperature,…:…
Current mirrors: using field-effect transistors only
Systems for regulating electric or magnetic variables
Term end not estimated
1. Field of the Invention
The present invention generally relates to a reference voltage source circuit used in analog circuits, etc., and in particular to a reference voltage source circuit that is able to operate with a low voltage.
2. Description of the Related Art
FIG. 1 is a diagram illustrating a reference voltage source circuit disclosed in citation 2;
FIG. 2A is a graphic representation illustrating a relation of temperature coefficients with respect to low concentration (Ng1);
FIG. 2B is a graphic representation illustrating a relation of temperature coefficients with respect to gate resistance;
The present invention is to realize, by a CMOS process, a reference voltage source circuit that operates with a low voltage and that can be used even in a strong inversion region, by using a pair of MOS transistors having gates of the same conduction type but of different impurity concentrations. Before going into the details of embodiments according to the present invention, the principle of the present invention is described below.
The threshold voltage Vt for causing a strong inversion state in a MOS transistor is expressed as:
Vt=φms−Qf/Cox+2φf−Qb/Cox (1)