1. A driver for shaping a drive signal, comprising:
a pre-emphasis circuit configured to emphasize a rising edge portion and a falling edge portion of the drive signal;
an offset adjustment circuit configured to apply a direct-current offset to the drive signal; and
an amplifier configured to amplify the drive signal with the direct-current offset adjusted by the adjustment circuit, wherein
the amplifier has an input-output characteristic with a nonlinear portion, and
the offset adjustment circuit adjusts the direct-current offset so that the drive signal is amplified in the nonlinear portion.
2. The driver according to claim 1, wherein
the offset adjustment circuit adjusts the direct-current offset so that the rising edge portion of the drive signal input to the amplifier is included in the nonlinear portion.
3. The driver according to claim 1, wherein
the drive signal is a differential signal including a normal phase signal and a reverse phase signal,
the offset adjustment circuit adjusts the normal phase signal and the reverse phase signal included in the differential signal according to direct-current offsets different from each other, and
the amplifier is a differential amplifier configured to differentially amplify the differential signal.
4. The driver according to claim 3, wherein
the offset adjustment circuit adjusts the direct-current offset of the normal phase signal so the direct-current offset of the normal phase signal is higher than the direct-current offset of the reverse phase signal.
5. The driver according to claim 3, wherein
the offset adjustment circuit adjusts the normal phase signal and the reverse phase signal included in the differential signal according to DC offsets opposite in direction to each other.
6. The driver according to claim 1, wherein
the pre-emphasis circuit branches the drive signal, and provides a delay difference between branched drive signals and adds the branched drive signals together, thereby symmetrically emphasizing the rising edge portion and the falling edge portion.
7. The driver according to claim 1, wherein
the offset adjustment circuit includes:
a capacitor configured to remove a direct-current offset of the drive signal; and
at least one of a variable resistor and a variable current source configured to provide a direct-current offset to the drive signal with the direct-current offset removed by the capacitor.
8. The driver according to claim 1, wherein
the offset adjustment circuit adjusts a direct-current offset of the drive signal with the rising edge portion and the falling edge portion emphasized by the pre-emphasis circuit.
9. The driver according to claim 1, wherein
the pre-emphasis circuit emphasizes the rising edge portion and the falling edge portion of the drive signal with the direct-current offset adjusted by the offset adjustment circuit, and
the amplifier is an amplifier provided in the pre-emphasis circuit.
10. An optical transmission apparatus comprising:
a pre-emphasis circuit configured to symmetrically emphasize a rising edge portion and a falling edge portion of a drive signal;
an offset adjustment circuit configured to apply a direct-current offset to the drive signal;
an amplifier configured to amplify the drive signal with the direct-current offset adjusted by the adjustment circuit; and
a light-emitting element configured to convert the drive signal into an optical signal, wherein
the amplifier has an input-output characteristic with a nonlinear portion, and
the offset adjustment circuit adjusts the direct-current offset so that the drive signal is amplified in the nonlinear portion.
11. The optical transmission apparatus according to claim 10, wherein
the offset adjustment circuit adjusts the direct-current offset so that the rising edge portion of the drive signal input to the amplifier is included in the nonlinear portion.
12. The optical transmission apparatus according to claim 10, wherein
the drive signal is a differential signal including a normal phase signal and a reverse phase signal,
the offset adjustment circuit adjusts the normal phase signal and the reverse phase signal included in the differential signal according to direct-current offsets different from each other, and
the amplifier is a differential amplifier configured to differentially amplify the differential signal.
13. The optical transmission apparatus according to claim 12, wherein
the offset adjustment circuit adjusts the direct-current offset of the normal phase signal so the direct-current offset of the normal phase signal is higher than the direct-current offset of the reverse phase signal.
14. The optical transmission apparatus according to claim 12, wherein
the offset adjustment circuit adjusts the normal phase signal and the reverse phase signal included in the differential signal according to DC offsets opposite in direction to each other.
15. The optical transmission apparatus according to claim 10, wherein
the pre-emphasis circuit branches the drive signal, and provides a delay difference between branched drive signals and adds the branched drive signals together, thereby symmetrically emphasizing the rising edge portion and the falling edge portion.
16. The optical transmission apparatus according to claim 10, wherein
the offset adjustment circuit includes:
a capacitor configured to remove a direct-current offset of the drive signal; and
at least one of a variable resistor and a variable current source configured to provide a direct-current offset to the drive signal with the direct-current offset removed by the capacitor.
17. The optical transmission apparatus according to claim 10, wherein
the offset adjustment circuit adjusts a direct-current offset of the drive signal with the rising edge portion and the falling edge portion emphasized by the pre-emphasis circuit.
18. The optical transmission apparatus according to claim 10, wherein
the pre-emphasis circuit emphasizes the rising edge portion and the falling edge portion of the drive signal with the direct-current offset adjusted by the offset adjustment circuit, and
the amplifier is an amplifier provided in the pre-emphasis circuit.
19. A method for shaping a drive signal, comprising:
emphasizing a rising edge portion and a falling edge portion of the drive signal;
applying a direct-current offset to the drive signal;
providing an amplifier with an input-output characteristic with a nonlinear portion;
amplifying the drive signal with the direct-current offset with the amplifier; and
adjusting the direct-current offset so that the drive signal is amplified in the nonlinear portion.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for analysing a gas flow likely to contain particles or suspended aerosols, said method comprising
a step of conducting an analysis of a flame produced in a burner of a spectrophotometric andor ionisation detection device,
said flame being generated by mixing said gas flow with a combustive gas, so as to obtain a combustion,
wherein a nephelometric andor a turbidimetric detection is made of said gas flow by illuminating said gas flow before said combustion with a light source emitting inside a range of wavelengths distinct from one used by said spectrophotometric andor ionisation detection device so as to obtain information about said particles which are used to adjust said spectrophotometric andor ionisation detection device and to count said particles, as well as to deduce a composition of said particles on the basis of said information and of information delivered by said spectrophotometric andor ionisation detection device.
2. Method according to claim 1, which further includes a measurement of fluorescence of the gas flow illuminated by said light source.
3. Method according to claim 2, wherein said light source functions in pulsed mode.
4. Method according to claim 1, wherein said nephelometric measurement is provided by said spectrophotometric andor ionisation detection device.
5. Apparatus for analysing a gas flow likely to contain particles or suspended aerosol, said device comprising
a spectrophotometric andor ionisation detection device having a burner wherein said gas is injected through an intake pipe and is mixed with a combustive gas so as to produce a flame, and
focusing means which focus light radiation emitted by said flame on an inlet orifice of a spectrophotometric mounting,
wherein said intake pipe comprises a transparent portion which is illuminated by a light source, and at least one optical sensor is placed in front of said transparent portion so as to cause a turbidimetric andor nephelometric detection of said flow gas,
said optical sensor being connected to a processor which receives information provided from said turbidimetric andor nephelometric detection,
said processor comprising means adjusting said spectrophotometric andor ionisation detection device and for counting said particles as well as for deducing a composition of said particles on the basis of said information and of information delivered by said spectrophotometric andor ionisation detection device.
6. Device according to claim 5, wherein a turbidimetric measuring sensor is placed in the axis of the source (38) on the side of the intake pipe opposite the latter.
7. Device according to claim 5, wherein said light source emits in the near infrared spectrum.
8. Device according to claim 5, wherein said spectrophotometric device is designed so as to carry out a nephelometric measurement of the gas flow illuminated by said light source.