Pyroelectric infrared ray sensor

• US 5,917,187 A
• Filed: 11/18/1997
• Issued: 06/29/1999
• Est. Priority Date: 09/12/1997
• Status: Expired due to Term

• Current Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Hatatani, Teruki, Sakamoto, Shinji, Fujimura, Toshio, Takada, Yuji
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Israel, Andrew
• Application Number:
  US08/972,907
• Time in Patent Office: 588 Days
• Field of Search: 250/338.3, 250/338.2
• US Class Current: 250/338.3
• CPC Class Codes: H03K 17/941 using an optical detector H03K17/968 takes precedence

Abstract

A pyroelectric infrared ray sensor includes a voltage amplifying circuit provided with a signal amplifying part having a non-inverting amplifier, with an integrating circuit, and with voltage dividing resistors connected at a position where an input V_IN to the voltage amplifying circuit and an output V_B of the integrating circuit are resistance-divided to a non-inverting input terminal of the signal amplifying part which is practically formed by an operating amplifier, wherein the signal amplifying part includes a low-pass filter formed by a resistor and a capacitor, whereby the electrostatic capacity of the required capacitor can be minimized, and the entire circuit can be minimized in size and also in manufacturing costs.

Claims

1. A pyroelectric infrared ray sensor in which an output pyroelectric current of a pyroelectric element is converted into a voltage signal, and the voltage signal only in a predetermined frequency band is amplified by a voltage amplifying circuit to be processed to provide a detection signal as an output;

wherein the voltage amplifying circuit comprises a signal amplifying part consisting of a non-inverting amplifier including a first operational amplifier to an inverting input end of which a first resistor is connected and between the inverting input end and an output end of which a feedback resistor and a first capacitor are connected in parallel;

an integrating circuit including a second operational amplifier to an inverting input end of which an output end of the signal amplifying part is connected through a second resistor, and between the inverting input end and an output end of which a second capacitor is connected; and

voltage-dividing resistors connected at a position where an output of the integrating circuit and an input to the voltage amplifying circuit are resistance-divided to a non-inverting input end of the signal amplifying part.

2. The sensor according to claim 1 which further comprises a high-pass filter provided on input side of the voltage amplifying circuit.

3. The sensor according to claim 1 which further comprises a low-pass filter provided on output side of the voltage amplifying circuit.

4. The sensor according to claim 2 wherein the high-pass filter comprises a differential circuit of a resistor and a third capacitor, the high resistor being large in the resistance-temperature characteristics.

5. The sensor according to claim 4 wherein the resistor is at least one of a non-doped polysilicon and a transistor on-resistor.

6. The sensor according to claim 1 which further comprises a current-voltage converting circuit provided between the pyroelectric element and the voltage amplifying circuit for converting the pyroelectric current from the pyroelectric element into the voltage signal, the current-voltage converting circuit comprising an operating amplifier, a DC feedback circuit for feeding a DC component back to the operating amplifier, and an AC feedback circuit for feeding an AC component back to the operating amplifier.

7. The sensor according to claim 1 which further comprises a three dimensional circuit block to at least both surfaces of which electronic parts forming at least the voltage amplifying circuit and the pyroelectric element are mounted, and a cylindrical can having an optical filter covering the pyroelectric element for housing therein the three dimensional circuit block.