Fault detector for paper webs

Claim 2

An amplification circuit for a photoelectric device, said circuit comprising a transistor connected across first and second terminal means adapted for connection across a first d.c. potential supply source, said transistor having a control electrode and further having first and second current-passing electrodes connected via connection means to said first and second terminal means respectively, a load means comprising a diode junction, said load means connected in series with said photoelectric device across third and fourth terminal means adapted for connection across a second d.c. potential supply source, said photoelectric device connected to said third terminal means and said load means connected to said fourth terminal means, means connecting said control electrode of said transistor to the junction between said load means and said photoelectric device, and output terminal means connected to said first current-passing electrode of said transistor for deriving an output potential therefrom, said transistor having diode junction characteristics substantially the same as those of the first-named said diode junction.

Claim 3

The amplification circuit of claim 1, wherein said photoelectric device comprises a phototransistor.

Claim 4

The amplification circuit of claim 1, wherein said transistor is a bipolar transistor having base, emitter and collector electrodes, the diode junction thereof being formed between said base and emitter electrodes, and means connecting said output terminal means to said collector electrode of said transistor.

Claim 5

The amplification circuit of claim 1 further comprising second load means connected between said first current-passing electrode of said transistor and said first terminal means.

Claim 6

The amplification circuit of claim 4 further comprising third load means connected between said second current-passing electrode of said transistor and said second terminal means.

Claim 7

The amplification circuit of claim 1, wherein said first and third terminal means are one and the same.

Claim 8

The amplification circuit of claim 5, further comprising capacitance means interconnecting said second current-passing electrode of said transistor and said fourth terminal means.

Claim 9

The amplification circuit of claim 3, further comprising a second transistor having base, emitter and collector electrodes, said base and collector electrodes being interconnected to form, in conjunction with said emitter electrode, said first-named diode junction.

Claim 10

The amplification circuit of claim 8, wherein the first-named said transistor and said second transistor have substantially the same diode junction characteristics.

Claim 11

An amplification circuit for a phototransistor, said circuit comprising a first transistor having base, collector and emitter electrodes, first, second and third load means, and a capacitance means; said collector electrode of said first transistor connected through said second load means to a first terminal means; said emitter electrode of said first transister connected through said third load means to a second terminal means; said first load means comprising a second transistor having identical electrical characteristics to those of said first transistor and having base, collector and emitter electrodes, said base and collector electrodes thereof being interconnected; said emitter electrodes of said second transistor connected to a fourth terminal means and, through said capacitance means, to said collector electrode of said first transistor; said collector electrode of said second transistor connected through said phototransistor to a third terminal means; said first and third terminal means being one and the same and said fourth terminal means adapted for connection to a reference ground potential, with respect to which said first terminal means is adapted for connection to a potential of first polarity and said second terminal means is adapted for connection to a second potential of opposite polarity to said first polarity; means connecting said collector electrode of said second transistor to said base electrode of said first transistor; and output terminal means connected to said collector electrode of said first transistor for deriving an output potential therefrom.

Claim 12

An amplification circuit for a phototransistor, said circuit comprising a first transistor having base, collector and emitter electrodes, first, second and third load means, and a capacitance means; said collector electrode of said first transistor connected through said second load means to a first terminal means; said emitter electrode of said first transister connected through said third load means to a second terminal means; said first load means comprising a second transistor having identical electrical characteristics to those of said first transistor and having base, collector and emitter electrodes, said base and collector electrodes thereof being interconnected; said emitter electrodes of said second transistor connected to a fourth terminal means and, through said capacitance means, to said collector electrode of said first transistor; said collector electrode of said second transistor connected through said phototransistor to a third terminal means; said first and third terminal means being one and the same and said fourth terminal means adapted for connection to a reference ground potential, with respect to which said first terminal means is adapted for connection to a potential of first polarity and said second terminal means is adapted for connection to a second potential of opposite polarity to said first polarity; means connecting said collector electrode of said second transistor to said base electrode of said first transistor; and output terminal means connected to said collector electrode of said first transistor for deriving an output potential therefrom.

Claim 13

The amplification circuit of claim 10, wherein said first and second polarities are respectively positive and negative with respect to said reference ground potential, each of said transistors being of NPN type.

Claim 14

The amplification circuit of claim 10, wherein said first and second polarity potentials are of substantially the same magnitude with respect to said reference ground potential.

Claim 15

Fault detector apparatus for a web of paper or like material, comprising a light source and an array of photoelectric devices spaced therefrom and aligned therewith for receiving light emitted thereby, said photoelectric devices responsive to rapid fluctuations in the light transmitted by said web passing between said photoelectric devices and said light source, each said photoelectric device having associated therewith an amplification circuit comprising a diode junction series connected with said photoelectric device between terminal means adapted for connection across a first d.c. potential supply source and an amplification transistor connected between terminal means adapted for connection across a second d.c. potential supply source, said amplification transistor having a control electrode and further having diode junction characteristics substantially the same as those of the first-named said diode junction, and means connecting said control electrode to the junction of said photoelectric device and the first-named said diode junction.

Claim 16

Fault detector apparatus for a web of paper or like material, comprising a light source and an array of photoelectric devices spaced therefrom and aligned therewith for receiving light emitted thereby, said photoelectric devices responsive to rapid fluctuations in the light transmitted by said web passing between said photoelectric devices and said light source, each said photoelectric device having associated therewith an amplification circuit comprising a diode junction series connected with said photoelectric device between terminal means adapted for connection across a first d.c. potential supply source and an amplification transistor connected between terminal means adapted for connection across a second d.c. potential supply source, said amplification transistor having a control electrode and further having diode junction characteristics substantially the same as those of the first-named said diode junction, and means connecting said control electrode to the junction of said photoelectric device and the first-named said diode junction.