SEMICONDUCTOR CIRCUIT AND CONSTANT VOLTAGE REGULATOR EMPLOYING SAME

• US 20120013396A1
• Filed: 06/30/2011
• Published: 01/19/2012
• Est. Priority Date: 07/15/2010
• Status: Active Grant

• Current Assignee: Nisshinbo Micro Devices Incorporated
• Original Assignee: Ricoh Company Limited
• Inventors: MORINO, Koichi, KASHIMA, Yuki, ITO, Masatoshi, SAKAI, Shimpei
• Granted Patent: US 8,525,580 B2
• Time in Patent Office: Days
• US Class Current: 327/540
• CPC Class Codes: G05F 3/24 wherein the transistors are of the field-effect type only G05F3/205, G05F3/26, G05F3/30 take precedence

Abstract

A semiconductor circuit includes a voltage regulator and a buffer transistor. The voltage regulator converts an input voltage input to an input terminal thereof into an output voltage output to an output terminal thereof. The buffer transistor is an n-channel depletion-mode metal-oxide semiconductor field effect transistor, disposed between the power supply terminal and the voltage regulator with a gate terminal thereof connected to the power supply terminal, a drain terminal thereof connected to the power supply terminal, and a source terminal thereof connected to the input terminal of the voltage regulator.

Claims

1. A semiconductor circuit for use in connection with a power supply terminal, the circuit comprising:

a voltage regulator to convert an input voltage input to an input terminal thereof into an output voltage output to an output terminal thereof; and

a buffer transistor, being an n-channel depletion-mode metal-oxide semiconductor field effect transistor, disposed between the power supply terminal and the voltage regulator with a gate terminal thereof connected to the power supply terminal, a drain terminal thereof connected to the power supply terminal, and a source terminal thereof connected to the input terminal of the voltage regulator.

2. The semiconductor circuit according to claim 1, further comprising a resistor disposed between the power supply terminal and the drain terminal of the buffer transistor.

3. The semiconductor circuit according to claim 1, further comprising:

a resistor disposed between the power supply terminal and the gate terminal of the buffer transistor; and

a capacitor disposed between a ground and the gate terminal of the buffer transistor.

4. The semiconductor circuit according to claim 1,

wherein the voltage regulator is implemented in an integrated circuit containing one or more circuit components integrated into a single integrated unit, at least one of the circuit components supplied with the output voltage regulated through the voltage regulator.

5. The semiconductor circuit according to claim 1, wherein the voltage regulator includes a driver transistor connected between the input and output terminals thereof,

the source terminal of the buffer transistor being connected solely to a conductive terminal of the driver transistor.

6. The semiconductor circuit according to claim 5, further comprising a resistor disposed between the power supply terminal and the drain terminal of the buffer transistor.

7. The semiconductor circuit according to claim 5, further comprising:

a resistor disposed between the power supply terminal and the gate terminal of the buffer transistor; and

a capacitor disposed between a ground and the gate terminal of the buffer transistor.

8. The semiconductor circuit according to claim 5,

wherein the voltage regulator is implemented in an integrated circuit containing one or more circuit components integrated into a single integrated unit, at least one of the circuit components being supplied with the output voltage regulated through the voltage regulator.

9. The semiconductor circuit according to claim 8,

wherein the driver transistor of the voltage regulator is an n-channel field effect transistor.

10. A voltage regulator for use in connection with a power supply terminal, the voltage regulator comprising:

an input terminal to receive an input voltage supplied from the power supply terminal;

an output terminal to output an output voltage to load circuitry;

a driver transistor connected between the input and output terminals to convert the input voltage into the output voltage; and

a buffer transistor, being an n-channel depletion-mode metal-oxide semiconductor field effect transistor, disposed between the power supply terminal and the voltage regulator with a gate terminal thereof connected to the power supply terminal, a drain terminal thereof connected to the power supply terminal, and a source terminal thereof connected to the input terminal of the voltage regulator.

11. The voltage regulator according to claim 10, wherein the source terminal of the buffer transistor is connected solely to a conductive terminal of the driver transistor.