Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Amplitude control
Reexamination Certificate
2001-09-19
2003-02-04
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Amplitude control
C327S108000, C326S083000
Reexamination Certificate
active
06515532
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the benefit of a Japanese Patent Application No. 2000-298969 filed Sep. 29, 2000, in the Japanese Patent Office.
1. Field of the Invention
The present invention generally relates to level shift circuits for converting a power supply voltage system of an input end to another power supply voltage system, and more particularly to a level shift circuit which shifts both levels of a high voltage power supply and a low voltage power supply of the power supply voltage system.
2. Description of the Related Art
FIG. 1
is a circuit diagram showing an example of a conventional level shift circuit.
In
FIG. 1
, a level shift circuit
100
includes an initial stage circuit section
101
and a final stage circuit section
102
. The initial stage circuit section
101
converts an input signal received via an input terminal IN into a signal having a high-level voltage of +5 V and having a low-level voltage of 0 V. The final stage circuit section
102
converts the output signal of the initial stage circuit section
101
into a signal having a high level which is shifted to a voltage of +10 V. The initial stage circuit section
101
is formed by inverter circuits
103
and
104
which are connected in series, and output signals of the inverter circuits
103
and
104
are supplied to the final stage circuit section
102
. A power supply voltage of +5 V is applied to a positive side power supply input terminal of each of the inverter circuits
103
and
104
, and a power supply voltage of 0 V is applied to a negative side power supply input terminal of each of the inverter circuits
103
and
104
.
On the other hand, the final stage circuit section
102
is formed by inverter circuits
105
and
107
, and P-channel MOS transistors (hereinafter simply referred to as PMOS transistors)
106
and
108
. The inverter circuit
105
receives the output signal of the inverter circuit
104
. In addition, a power supply voltage of +10 V is applied to a positive side power supply input terminal of the inverter circuit
105
via the PMOS transistor
106
, and a power supply voltage of 0 V is applied to a negative side power supply input terminal of the inverter circuit
105
. Similarly, the inverter circuit
107
receives the output signal of the inverter circuit
103
. In addition, the power supply voltage of +10 V is applied to a positive side power supply input terminal of the inverter circuit
107
via the PMOS transistor
108
, and the power supply voltage of 0 V is applied to a negative side power supply input terminal of the inverter circuit
107
. An output signal of the inverter circuit
107
is applied to a gate of the PMOS transistor
106
, and an output signal of the inverter circuit
105
is applied to a gate of the PMOS transistor
108
.
The output signal of the inverter circuit
104
is subjected to a level shift by the inverter circuit
105
and the PMOS transistor
106
, so that a high-level voltage is level-shifted to +10 V and output from an output terminal OUT
1
Similarly, the output signal of the inverter circuit
103
is subjected to a level shift by the inverter circuit
107
and the PMOS transistor
108
, so that a high-level voltage is level-shifted to +10 V and output from an output terminal OUT
2
.
However, according to this conventional level shift circuit, it is only possible to shift the level of the high-level voltage or the low-level voltage of the input signal. For this reason, in order to shift the level of both the high-level voltage and the low-level voltage of the input signal, it is necessary to provide another level shift circuit. In other words, in the case where the level shift circuit
100
is used to shift the level of the high-level voltage of the input signal, it is necessary to provide another level shift circuit to soft the level of the low-level voltage of the input signal. Therefore, there was a problem in that two level shift circuits were necessary in order to shift the level of both the high-level voltage and the low-level voltage of the input signal.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful level shift circuit in which the problem described above is eliminated.
Another and more specific object of the present invention is to provide a level shift circuit which can shift the level of both a high-level voltage and a low-level voltage of an input signal.
Still another object of the present invention is to provide a level shift circuit comprising an initial stage circuit section, including a first inverter circuit portion coupled to a first high voltage power supply and to a first low voltage power supply, converting an input signal into a signal having a voltage level of the first high voltage power supply as a high level and a voltage level of the first low voltage power supply as a low level; an intermediate stage circuit section, including a second inverter circuit portion coupled to the first high voltage power supply and to a second low voltage power supply which supplies a voltage level lower than the first low voltage power supply, level-shifting the signal output from the initial stage circuit section into a signal having the voltage level of the first high voltage power supply as a high level and the voltage level of the second low voltage power supply as a low level, in response to the signal output from the initial stage circuit section; and a final stage circuit section, including a third inverter circuit portion coupled to the second low voltage power supply and to a second high voltage power supply which supplies a voltage level higher than the first high voltage power supply, level-shifting the signal output from the intermediate stage circuit section into a signal having the voltage level of the second high voltage power supply as a high level and the voltage level of the second low voltage power supply as a low level, in response to the signal output from the intermediate stage circuit section. According to the level shift circuit of the present invention, it is possible to shift the level of both a high-level voltage and a low-level voltage of an input signal by use of a simple circuit structure.
The intermediate stage circuit section may include an output end, and the second inverter circuit portion may include a first transistor coupled between the first high voltage power supply and the output end and responsive to the signal output from the initial stage circuit section, and a second transistor coupled between the output end and the second low voltage power supply. In this case, the second transistor of the second inverter circuit portion may have a control signal input terminal, and the level shift circuit may further comprise a voltage generating circuit which generates a voltage which is applied to the control signal input terminal of the second transistor.
Further, the voltage generating circuit may apply the voltage generated thereby to the second transistor of the second inverter circuit portion when each transistor within the second inverter circuit portion is in a ratioed state.
In addition, the voltage generating circuit may apply the voltage generated thereby to the second transistor of the second inverter circuit portion, so that a ratio of a first resistance between the first high voltage power supply and the second low voltage power supply and a second resistance between the output end of the intermediate stage circuit section and the second low voltage power supply,becomes a predetermined value.
A further object of the present invention is to provide a level shift circuit comprising an initial stage circuit section, coupled to a first high voltage power supply and to a first low voltage power supply, converting an input signal into a signal having a voltage level of the first high voltage power supply as a high level and a voltage level of the first low voltage power supply as a low level; an intermediate stage circuit section, coupled to the first high voltage
Dickstein , Shapiro, Morin & Oshinsky, LLP
Ricoh & Company, Ltd.
Wells Kenneth B.
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