Semiconductor integrated circuit device

• US 7,173,476 B2
• Filed: 02/24/2004
• Issued: 02/06/2007
• Est. Priority Date: 02/26/2003
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Yamamoto, Seiichi, Maeda, Norihiro, Ueda, Toyokazu
• Primary Examiner(s): Lam; Tuan T.
• Assistant Examiner(s): Nguyen; Hiep
• Application Number:
  US10/784,302
• Publication Number:
  US 20040164786A1
• Time in Patent Office: 1,078 Days
• Field of Search: 327/112, 327/322, 327/577, 323/285, 323/284
• US Class Current: 327/427
• CPC Class Codes: G05F 3/262 using field-effect transistors only
• CPC Class Codes: H03K 17/0822 in field-effect transistor switches

Abstract

The drain of a power transistor M1 is connected to the non-inverting input terminal of an operational amplifier A and the drain of a transistor M2 is connected to the inverting input terminal of the operational amplifier A to make substantially equal the drain voltages of the power transistor M1 and the transistor M2, of which the gates are connected together and of which the sources are connected together. The drain current of the transistor M2 is outputted via a detection terminal 13 as a current signal proportional to the drain current of the power transistor M1.

Claims

1. A semiconductor integrated circuit device comprising:

a power transistor that feeds a large current to a load;

a first transistor of which a second electrode and a control electrode are connected respectively to a second electrode and a control electrode of the power transistor;

a second transistor of which a second electrode is connected to a first electrode of the first transistor; and

a third transistor of which a control electrode is connected to a first electrode of the power transistor and of which a second electrode is connected to a control electrode of the second transistor,

wherein the second transistor outputs, at a first electrode thereof, a current signal proportional to a current flowing through the power transistor.

2. A semiconductor integrated circuit device as claimed in claim 1,

wherein a first electrode of the third transistor is connected to the second electrodes of the power transistor and the first transistor, and a direct-current voltage is applied through a resistor to the second electrode of the third transistor.

3. A semiconductor integrated circuit device as claimed in claim 1,

wherein the second and third transistors are transistors of opposite polarities, and a potential difference appearing between the second electrode and control electrode of the second transistor is substantially equal to a potential difference appearing between the second electrode and control electrode of the third transistor.

4. A semiconductor integrated circuit device as claimed in claim 3, wherein the second transistor is a transistor of a same polarity as the first transistor.

5. A semiconductor integrated circuit device as claimed in claim 4,

wherein a first electrode of the third transistor is connected to the second electrodes of the power transistor and the first transistor, and a direct-current voltage is applied through a resistor to the second electrode of the third transistor.