Circuit for varying gain of preamplifier
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsMasamichi Nogami, Masaki Noda, Hitoyuki Tagami, Kuniaki Motoshima
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Abstract
A gain switching circuit switches a conversion gain of a preamplifier that is configured with a series circuit formed with a first resistor and a first switching element and a series circuit formed with a second resistor and a second switching element respectively connected in parallel with a feedback resistor. The gain switching circuit includes a first operating unit that generates a first switching element operating signal for closing the first switching element within a first gain switching period, and a second operating unit that generates a second switching element operating signal for closing the second switching element within a second gain switching period.
Claims9
A gain switching circuit configured to switch a conversion gain of a preamplifier, the preamplifier being configured to output a voltage signal by amplifying an output current of a photo-detecting element configured to convert a burst optical signal into an electrical signal, the preamplifier being configured with a first series circuit formed with a first resistor and a first switching element and a second series circuit formed with a second resistor and a second switching element respectively connected in parallel with a feedback resistor, the gain switching circuit inputting a first gain switching signal defining a period for switching to a first conversion gain and a second gain switching signal defining a period for switching to a second conversion gain, said first gain switching signal and said second gain switching signal originating from outside of the gain switching circuit, the gain switching circuit comprising:
- a first operating unit configured to generate a first switching element operating signal to close the first switching element in response to the voltage signal output by the preamplifier being above a first threshold during the period defined by the first gain switching signal originating from outside the gain switching circuit;
- and
- a second operating unit configured to generate a second switching element operating signal to close the second switching element in response to the voltage signal output by the preamplifier being above a second threshold during the period defined by the second gain switching signal originating from outside the gain switching circuit.
A gain switching circuit configured to switch a conversion gain of a preamplifier, the preamplifier being configured to output a voltage signal by amplifying an output current of a photo-detecting element configured to convert a burst optical signal into an electrical signal, the preamplifier being configured with a first series circuit formed with a first resistor and a first switching element and a second series circuit formed with a second resistor and a second switching element respectively connected in parallel with a feedback resistor, the gain switching circuit comprising:
- a gate generating circuit configured to generate a gate signal defining a period for switching to a predetermined conversion gain;
- a first operating unit configured to generate a first switching element operating signal to close a first switching element in response to the voltage signal output by the preamplifier being above a first threshold during the period defined by the gate signal generated by the gate generating circuit;
- and
- a second operating unit configured to generate a second switching element operating signal to close a second switching element in response to the voltage signal output by the preamplifier being above a second threshold during the period defined by the gate signal generated by the gate generating circuit.
Dependencies are inferred from the claim text.