Input circuit for infrared detector
First Claim
1. An input circuit for a multichannel infrared detection system comprising a bias network connectable to the output of an external power supply, and a plurality of detector channels, each of said channels being connectable to a dedicated detector element and having at least one semiconductor device commonly connected to said bias network, said detector channels and said bias network being formed on a common semiconductor substrate, said bias network including circuitry to reduce power level variations present in the output from the external power supply and to thereby generate a low level bias signal, said bias signal being sufficient to bias at least one detector channel semiconductor device in each detector channel into a linear region of operation.
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Abstract
A method and circuit are provided for interfacing an infrared detector to a common power supply and signal processing circuitry. A multichannel input circuit including a plurality of buffer circuits and a common bias network is formed on a single semiconductor substrate. The common bias network reduces the necessary connections between the substrate and the external power supply. The bias network is operative to reduce power level variations in the signal from the external power supply. Each channel includes a negative feedback circuit to maintain a dedicated detector in a zero bias condition, thus reducing 1/f noise and enhancing the signal-to-noise ratio of the circuit. The load to each channel is adjustable to maintain the detector in the zero bias condition.
38 Citations
19 Claims
- 1. An input circuit for a multichannel infrared detection system comprising a bias network connectable to the output of an external power supply, and a plurality of detector channels, each of said channels being connectable to a dedicated detector element and having at least one semiconductor device commonly connected to said bias network, said detector channels and said bias network being formed on a common semiconductor substrate, said bias network including circuitry to reduce power level variations present in the output from the external power supply and to thereby generate a low level bias signal, said bias signal being sufficient to bias at least one detector channel semiconductor device in each detector channel into a linear region of operation.
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14. A method of generating signal levels for providing low level biasing for a multichannel infrared detection circuit, the method comprising the steps of:
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receiving a signal from an external power source at the input of a common bias network for a multichannel infrared detection circuit, said bias network and each channel of said multichannel detector circuit being formed on a common semiconductor substrate; commonly connecting each channel of said multichannel bias circuit to an output of said bias network, said common connections being effective to collectively load said bias network into a linear operational condition; reducing power level variations in said received signal to form a low level bias signal for communication to each of said channels; and communicating said low level bias signal to each of said detector channels, said bias signal being sufficient to bias each of said channels into a linear operational region. - View Dependent Claims (15, 16, 17, 18)
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19. A method of generating a signal in response to irradiation of an infrared detector comprising the steps of:
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receiving a signal from external power supply at the input of a common bias network of a multichannel infrared detection circuit, said bias network and each channel of said multichannel detector circuit being formed on a common semiconductor substrate, each of said channels comprising an input FET, a load FET and a feedback FET; connecting a first lead of a dedicated infrared detector to the gate of said input FET, said input FET having a source connected to a common output of said bias network and a drain connected to both the source of said load FET and to the gate of said feedback FET, said input FET in each of said channels receiving approximately the same bias signal from said bias network, said bias signal being sufficient to bias said input FET in each of said channels into a linear operational condition; connecting a second lead of said detector to a reference voltage; connecting the source of said feedback FET to the gate of said input FET; connecting a storage device between the gate and source of said load FET; temporarily shorting the gate of said input FET to said reference voltage so as to provide zero volts across said detector; temporarily shorting the gate and drain of said load FET; disconnecting the gate of said input FET from said reference voltage; disconnecting the short between the gate and drain of said load FET so as to bias said load FET to operate as a constant current load to said input FET, the level of said constant current load being equal to the current through said input FET when the base of said input FET is at said reference voltage; irradiating said detector with infrared frequency energy; feeding back to the gate of said feedback FET the portion of the current through said input FET in excess of said constant curent load level; and generating an output from said feedback FET in response to said fedback current.
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Specification