Back bias voltage level detector

Details Back bias voltage level detector Back bias voltage level detector

1998-09-08

2001-01-02

Callahan, Timothy P. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific signal discriminating without subsequent control

By amplitude

C327S318000, C327S325000, C327S538000

Utility Patent

active

06169426

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a back bias voltage level detector, and particularly to an improved back bias voltage level detector which is capable of detecting a back bias voltage even though an electric voltage Vcc is varied.
2. Description of the Background Art
FIG. 1
illustrates a known back bias voltage level detector. As shown therein, the known back bias voltage level detection includes resistors R1 and R2 connected in series between an electric voltage Vcc and a back bias voltage Vbb, and a comparator OP in which a node A connected with each one terminal of the resistors R
1
and R2 is connected with a non-inverted terminal of the comparator OP and a reference voltage Vref is inputted into an inverted terminal of the same.
The operation of the known back bias voltage level detector will now be explained with reference to the accompanying drawings.
First, as shown in
FIG. 1
, the serially connected resistors R
1
and R2 serve to distribute the electric voltage Vcc and limit the electric voltage. Therefore, the voltage V
1
of the node A is obtained by the following equation 1, and the back bias voltage Vbb based on the voltage V
1
is obtained by the following equation 2.
V1
=
R2
R1
+
R2
⁢
(
Vcc
-
Vbb
)
[
Equation
⁢
 
⁢
1
]
Vbb
=
Vcc
-
R1
+
R2
R2
⋆
V1
[
Equation
⁢
 
⁢
2
]
In addition, the comparator OP outputs the input voltage V
1
when the input voltage V
1
inputted into the non-inverted terminal of the comparator OP is identical with the reference voltage Vref, so that the back bias voltage is detected and outputted through an output terminal Vout.
FIG. 2
is a graph illustrating the variation of a back bias voltage level of the circuit of FIG.
1
.
However, in the known back bias voltage level detector, if the electric voltage Vcc is varied, as shown in
FIG. 2
, the input voltage Vi inputted into the comparator OP is also varied thereby. Namely, in accordance with Equations 1 and 2, the input voltage V1 is varied proportionally to the electric voltage Vcc. Therefore, it is impossible to accurately detect the back bias voltage level.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a back bias voltage level detector which overcomes the aforementioned problems encountered in the background art.
It is another object of the present invention to provide a back bias voltage level detector which is capable of accurately detecting a back bias voltage level by constantly maintaining a voltage inputted into a comparator using a clamp circuit or a current mirror circuit.
To achieve the above objects, there is provided a back bias voltage level detector which includes a voltage controller for accurately detecting the back bias voltage and constantly maintaining a voltage inputted into the comparator wherein the back bias voltage level detector includes first and second resistors connected in series between an electric voltage and a back bias voltage for distributing a voltage inputted, a comparator comparing the voltage distributed and inputted thereinto with a reference voltage wherein a back bias voltage detector is provided for outputting a detection signal to the outside by judging that a predetermined back bias voltage is detected when the input voltage and the reference voltage are identical as a result of the comparison.
In order to accurately detect a back bias voltage, there is provided a clamp circuit or a current mirror circuit which is capable of constantly maintaining a voltage inputted into the comparator.
Additional advantages, objects and features of the invention will become more apparent from the description which follows.


REFERENCES:
patent: 5184030 (1993-02-01), Chung et al.
patent: 5336943 (1994-08-01), Kelly et al.
patent: 5719533 (1998-02-01), Shibuya et al.

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