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Pyroelectric sensor with high sensitivity

  • US 4,868,390 A
  • Filed: 02/16/1988
  • Issued: 09/19/1989
  • Est. Priority Date: 02/16/1988
  • Status: Expired due to Fees
First Claim
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1. A pyroelectric sensor element having a high sensitivity to radiation and a low noise output signal, comprising:

  • a power source having positive and negative terminals;

    a pyroelectric element having a piece of pyroelectric material connected between two electrodes to develop an electrical signal across said electrodes responsive to radiation incident on said material;

    a current amplifier in the form of a first operational amplifier connected to said power source and having a first input terminal connected directly to one of said electrodes, a second input terminal for receiving a reference voltage signal, and an output terminal;

    said current amplifier including a feedback resistor connected between said output terminal and said first input terminal of high resistance so that amplifier noise is negligible;

    a compensation amplifier in the form of a second operational amplifier connected to said power source and having a first input terminal connected directly to said one electrode, and an output terminal; and

    discrete circuit component means connected directly between said output terminal of said compensation amplifier and said first input terminal of said first operational amplifier, said compensation amplifier being operational and said component means functioning to inhibit input current noise to said current amplifier for protecting said current amplifier from overloading when the voltage of said electrode exceeds the voltage of said positive terminal or falls below the voltage of said negative terminal by acting to maintain the voltage at said first input terminal of said current amplifier at substantially the same voltage as the voltage at said output terminal of said compensation amplifier, with minimum voltage drop across said component means and minimum noise-generating current flow therethrough.

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