Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Particular stable state circuit
Reexamination Certificate
2000-05-08
2001-10-23
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Particular stable state circuit
C327S359000
Reexamination Certificate
active
06307415
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electronic circuits used to generate timing signals and more specifically to circuits used to generate a stable and monostable multivibrator such as '555 type timers.
2. Description of the Relevant Art
The problem addressed by this invention is encountered in circuits used for generating astable multivibrators. Astable multivibrators are commonly used, in combination with resistors and a capacitor to generated a square wave type signal. Such a square wave signal is used in many systems including computers, consumer electronic products, and automobiles.
A timer circuit that has a wide rage of astable and monostable possibilities is the low-power CMOS version of the 555 timer, manufactured as either an L555, XR555, or ICM7556.
FIG. 1
shows the block diagram of an industry standard L555 as is known in the prior art. The circuit includes a comparator
2
, a comparator
4
, and a RS flip-flop
6
. The RS flip-flop is typically constructed out of two nor gates, also shown in
FIG. 1
as nor gates
8
and
10
.
FIG. 2
shows how the output Q is a function of the IN, IN+, and IN− inputs. These inputs can be controlled to determine the hystersis of the circuit.
FIG. 3
shows in detail the prior art circuit typically used to implement the block diagram of the 555 timer circuit. Transistors
12
-
28
are configured as a typical comparator which corresponds to comparator
2
of FIG.
1
. Similarly, transistors
30
-
46
correspond to comparator
4
of FIG.
1
. Transistors
48
-
54
correspond to nor gate
8
and transistors
56
-
62
correspond to nor gate
10
, both of FIG.
1
. Resistor
64
and transistor
66
are necessary to provide the bias voltage to transistors
24
and
42
.
FIG. 3
also shows that
27
transistors are needed to use this circuit.
Therefore, it is an objects of the invention to reduce the number of transistors used to make a timer circuit.
It is another object of the invention reduce the cost of a timer circuit by decreasing the number of transistors in the circuit.
It is and yet another object of the invention to increase the reliability of the circuit by decreasing the number of transistors in the circuit.
These and other objects, features, and advantages of the invention will be apparent to those skilled in the art from the following detailed description of the invention, when read with the drawings and appended claims.
SUMMARY OF THE INVENTION
The invention can be summarized as a timer circuit having two differential pairs of transistors, three current mirrors, two selectable current sources, and one inverter. The two differential pairs of transistors, three current mirrors, two selectable current sources, and one inverter are arranged to receive an IN+ voltage, an IN voltage, and a IN− voltage. From these inputs a Q and Q(bar) output is generated. This timing circuit can be used to generate an oscillator by connecting a capacitor, a current source, and current drain to the IN voltage.
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patent: 4947140 (1990-08-01), Tateishi
patent: 5268872 (1993-12-01), Fujii et al.
patent: 5276369 (1994-01-01), Hayakawa et al.
patent: 5311150 (1994-05-01), Engbretson et al.
patent: 5446396 (1995-08-01), Brehmer
patent: 5495207 (1996-02-01), Novof
patent: 5528185 (1996-06-01), Lewicki et al.
patent: 6127868 (2000-10-01), Phillips
patent: 0 180 084 A2 (1986-05-01), None
patent: 0 577 887 A1 (1994-01-01), None
Wigmore “More Applications For The 555,”Elektor Electronics, (No. 164):pp. 24-28, 1989.
Lancaster, “Chapter 4: Multivibrators,”CMOS Cookbook, 2d ed., Prentice Hall Computer Publishing, pp. 297-304, 1993.
Carlson David V.
Galanthay Theodore E.
Jorgenson Lisa K.
STMicroelectronics Inc.
Wells Kenneth B.
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