Input protection circuit

• US 20050017796A1
• Filed: 07/15/2004
• Published: 01/27/2005
• Est. Priority Date: 07/22/2003
• Status: Abandoned Application

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Tanizawa, Yukihiko
• Application Number:
  US10/891,005
• Publication Number:
  US 20050017796A1
• Time in Patent Office: Days
• US Class Current: 327/562
• CPC Class Codes: H03F 1/523 for amplifiers using field-effect devices H03F1/526 takes precedence

Abstract

An input protection circuit installed within a non-inverted amplifier includes a first diode with one end electrically connected to the non-inverted input terminal of the non-inverted amplifier and the other end electrically connected to the base voltage and a second diode having a cathode electrically connected to a power voltage of the non-inverted amplifier and an anode connected to the base voltage.

Claims

1. An input protection circuit installed within a non-inverted amplifier comprised of an operational amplifier that has an input signal on a non-inverted input terminal, a first resistor electrically connected between an output terminal and an inverted terminal of the operational amplifier, and a second resistor with one terminal electrically connected to the inverted terminal of the operational amplifier and the other terminal electrically connected to a base voltage of the input signal, wherein the input signal is raised to a predetermined high voltage higher than the ground level, wherein the input protection circuit comprises:

a first diode with one end electrically connected to the non-inverted input terminal of the non-inverted amplifier and the other end electrically connected to the base voltage; and

a second diode having a cathode electrically connected to a power voltage of the non-inverted amplifier and an anode connected to the base voltage.

2. An input protection circuit according to claim 1, further comprising a third diode having a cathode connected to the base voltage and an anode electrically connected to the ground voltage.

3. An input protection circuit according to claim 1, further comprising:

a first protection resistor with one end electrically connected to the non-inverted input terminal; and

a second protection resistor with one end electrically connected to the base voltage, wherein a signal voltage of the input signal is applied electrically between the other ends of the first and second protection resistors.

4. An input protection circuit according to claim 1, wherein the operational amplifier is a MOS input operational amplifier comprised of first and second transistors to form a differential input circuit in an input stage, wherein the first and second transistors respectively receive non-inverted input and inverted input.

5. A non-inverted amplifier comprising:

an operational amplifier that has an input signal on a non-inverted input terminal;

a first resistor electrically connected between an output terminal and an inverted terminal of the operational amplifier;

a second resistor with one terminal electrically connected to the inverted terminal of the operational amplifier and the other terminal electrically connected to a base voltage of the input signal, wherein the input signal is raised to a predetermined high voltage higher than the ground level; and

an input protection circuit comprised of a first diode with one end electrically connected to the non-inverted input terminal of the non-inverted amplifier and the other end electrically connected to the base voltage; and

a second diode having a cathode electrically connected to a power voltage of the non-inverted amplifier and an anode connected to the base voltage.