DIFFERENTIAL AMPLIFIER CIRCUIT, OPERATIONAL AMPLIFIER INCLUDING DIFFERENCE AMPLIFIER CIRCUIT, AND VOLTAGE REGULATOR CIRCUIT

• US 20110181358A1
• Filed: 01/20/2011
• Published: 07/28/2011
• Est. Priority Date: 01/27/2010
• Status: Active Grant

• Current Assignee: RICOH Electronic Devices Co., Ltd. (Nisshinbo Holdings Incorporated)
• Original Assignee: Ricoh Company Limited
• Inventors: AISU, Katsuhiko
• Granted Patent: US 8,378,747 B2
• Time in Patent Office: Days
• US Class Current: 330/257
• CPC Class Codes: H03F 2203/45526 the FBC comprising a resistor-capacitor combination and being coupled between the LC and the IC
• CPC Class Codes: H03F 3/45188 Non-folded cascode stages

Abstract

A differential amplifier circuit includes a differential input stage comprising first and second transistors whose sources are connected with each other, a constant current source connected between the sources of the first and second transistors and a ground, a current mirror circuit comprising third and fourth transistors whose sources are connected with a power supply source, a fifth transistor of a same conductive type as that of the first transistor, connected at a drain to a drain of the third transistor, connected at a source to a drain of the first transistor and connected at a gate to a reference voltage source; and a sixth transistor of a same conductive type as that of the second transistor, connected at a drain to a drain of the fourth transistor, connected at a source to a drain of the second transistor, and connected at a gate to the reference voltage source.

Claims

1. A differential amplifier circuit comprising:

a differential input stage comprising first and second transistors whose sources are connected with each other;

a constant current source connected between the sources of the first and second transistors and a ground;

a current mirror circuit comprising third and fourth transistors whose sources are connected with a power supply source;

a fifth transistor of a same conductive type as that of the first transistor, connected at a drain to a drain of the third transistor, connected at a source to a drain of the first transistor and connected at a gate to a reference voltage source; and

a sixth transistor of a same conductive type as that of the second transistor, connected at a drain to a drain of the fourth transistor, connected at a source to a drain of the second transistor, and connected at a gate to the reference voltage source.

2. An operational amplifier comprising

a differential amplifier circuit which comprises:

a differential input stage comprising first and second transistors whose sources are connected with each other;

a constant current source connected between the sources of the first and second transistors and a ground;

a current mirror circuit comprising third and fourth transistors whose sources are connected with a power supply source;

a fifth transistor of a same conductive type as that of the first transistor, connected at a drain to a drain of the third transistor, connected at a source to a drain of the first transistor and connected at a gate to a reference voltage source; and

a sixth transistor of a same conductive type as that of the second transistor, connected at a drain to a drain of the fourth transistor, connected at a source to a drain of the second transistor, and connected at a gate to the reference voltage source.

3. A voltage regulator circuit comprising

an operational amplifier as an error amplifier, the operational amplifier comprising a differential amplifier circuit which comprises:

a differential input stage comprising first and second transistors whose sources are connected with each other;

a constant current source connected between the sources of the first and second transistors and a ground;

a current mirror circuit comprising third and fourth transistors whose sources are connected with a power supply source;

a fifth transistor of a same conductive type as that of the first transistor, connected at a drain to a drain of the third transistor, connected at a source to a drain of the first transistor and connected at a gate to a reference voltage source; and

a sixth transistor of a same conductive type as that of the second transistor, connected at a drain to a drain of the fourth transistor, connected at a source to a drain of the second transistor, and connected at a gate to the reference voltage source.

4. A voltage regulator circuit according to claim 3, further comprising a low pass filter at an input of the differential input stage.