Current-boosted positive feedback logarithmic transresistance amplifier for currency validators
AssigneeArdac, Inc.
InventorsClaude Abraham, Philip C. Dolsen
Life of this patent
Estimating the term…
Abstract
A current boosted positive feedback logarithmic transresistance amplifier is provided for currency validators. The amplifier has a photo-diode capable of producing a current in response to light, connected to an operational amplifier having both a positive and a negative feedback branch. A logarithmic density amplifier having a feedback resistor and a log diode connected in shunt with the resistor as a dynamic feedback to the amplifier is connected to the positive feedback branch of the current boosting amplifier by way of the log diode. The summing action at the inputs of the current boosting amplifier result in a current at the log diode that is a direct multiple of the current in the photo-diode.
Claims17
In an optical density sensing circuit for security validators, the sensing circuit having a photo-diode capable of producing a current in response to light, the photodiode connected to a first amplifier, the first amplifier having an dynamic feedback branch, the dynamic feedback branch including a feedback resistor, and a log diode connected in shunt with the feedback resistor, the improvement comprising:
- a mixed feedback current boosting means for providing a current to the log diode, said current being a direct multiple of the current in the photo-diode.
An optical density sensing circuit for a security validator, comprising:
- a photo-diode capable of producing a current in response to light;
- a first amplifier connected to said photo-diode, said first amplifier having a dynamic feedback branch including a feedback resistor and a log diode;
- and
- a mixed feedback current boosting amplifier for providing a current to the log diode, said current being a direct multiple of the current in the photo-diode.
A current boosting amplifier for providing a current to the log diode of a logarithmic amplifier from a photo-diode, comprising a positive feedback branch and a negative feedback branch, the photo-diode being connected between said positive and negative feedback branches.
Dependencies are inferred from the claim text.