US 2009/0015299 A1Published application

Output circuit

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsTakashi RYU, Takuya Ishii, Naoyuki Nakamura, Hiroshisa Tanabe

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Abstract

A reference voltage is applied from a reference voltage generating circuit to the non-inverting input terminal of an amplifier for supplying a drive voltage to the gate terminal of an NMOS transistor, and the output voltage appearing at the source terminal of the NMOS transistor is divided by a resistor pair and applied to the inverting input terminal of the amplifier. The voltage obtained by adding a voltage equal to or higher than the voltage for sufficiently driving the NMOS transistor to the output voltage appearing at the source terminal of the NMOS transistor is generated by a charge pump circuit and supplied to the amplifier as a power supply voltage. With this configuration, the drive voltage for the NMOS transistor is suppressed to the required minimum voltage while the drive voltage is obtained securely. The power consumption in the amplifier can thus be suppressed.

Claims11

Dependent claims

An output circuit comprising:

an output transistor having one main terminal to which an input voltage is input, the other main terminal from which an output voltage is output and a control terminal, wherein a drive voltage being equal to or higher than the drive threshold voltage with reference to the potential of the other main terminal is applied to the control terminal, whereby the impedance between the one main terminal and the other main terminal can be controlled;
a control drive circuit for supplying said drive voltage to the control terminal of said output transistor to control the output voltage from the other main terminal of said output transistor;
and
a charge pump circuit, configured so as to output a predetermined voltage being equal to or higher than said drive threshold voltage with reference to the potential of the other main terminal of said output transistor, for supplying the power supply voltage obtained by adding the predetermined voltage being equal to or higher than said drive threshold voltage to the output voltage from the other main terminal of said output transistor.

1 more element

An output circuit comprising:

an output transistor having one main terminal to which an input voltage is input, the other main terminal from which an output voltage is output and a control terminal, wherein a drive voltage being equal to or higher than the drive threshold voltage with reference to the potential of the other main terminal is applied to the control terminal, whereby the impedance between the one main terminal and the other main terminal can be controlled;
a control drive circuit for supplying said drive voltage to the control terminal of said output transistor to control the output voltage from the other main terminal of said output transistor;
and
a charge pump circuit, configured so as to output a voltage with reference to the potential of the one main terminal of said output transistor, for carrying out control so that the power supply voltage supplied to said control drive circuit is the voltage obtained by adding a predetermined voltage being equal to or higher than said drive threshold voltage to the output voltage from the other main terminal of said output transistor.

1 more element

Dependencies are inferred from the claim text.