Santa Barbara Research Center

John A Stineman

Alan W Hoffman

Todd E Sessler

Kevin L Pettijohn

Mark A Goodnough

Method and apparatus for performing a TDI function with a plurality of electrical signals. A first step of the method stores, during individual ones of a first plurality of consecutive time intervals, a sample of a first electrical signal. A second step of the method equilibrates, during individual ones of a second, subsequent plurality of time intervals, one of the stored samples with a stored sample of a second electrical signal. Subsequent to each of the steps of equilibrating, an electrical signal is outputted that has a magnitude expressive of the equilibrated stored samples. The equilibration is achieved by shorting storage capacitors (C.sub.1, C.sub.2, C.sub.3) together to effectively sum coherent signals and incoherent noise. The charge sum is stored on a capacitance that is effectively doubled from either detector channel operating individually. The output signal remains in the same range as would be an individual detector channel output voltage, without TDI, and no reduction in dynamic range is incurred.

Hold capacitor time delay and integration with equilibrating means

A current mirror circuit 10 is coupled to a first and a second photodetector 18 and 20 and differentially couples together the two photodetectors to an amplifier 12 such that a resulting differential output current is independent of the intrinsic responsivity difference between the two photodetectors. The circuit includes a first transistor 14 having an input terminal coupled to an output terminal of the first photodetector and a second transistor 16 having an input terminal coupled to an output terminal of the second photodetector. A capacitance 22 is coupled between a control terminal of the first transistor and a control terminal of the second transistor, the control terminal of the first transistor further being coupled to the input terminal of the first transistor. A first switch 24 is coupled between the control terminal of the second transistor and the input terminal of the second transistor. A second switch 26 is coupled between the second transistor input terminal and an input of the transimpedance amplifier for coupling the output current signal to the transimpedance amplifier. Preferrably the transistors are MOSFETs operated in subthreshold. During calibration the first switch is closed and the photodetectors are illuminated by a reference flux. A voltage stored across the capacitance is shown to be expressive of the difference in threshold voltage between the two MOSFETs and also the logarithm of the ratio of detector responsivities.

Differential offset corrected current mirror

A read-out amplifier (200) for a photovoltaic detector (201) employs an integrating amplifier (203) with capacitor feedback (230 ) during a self-calibrating active load (205, 240) to minimize debiasing of the photovoltaic detector during its operation. The self-calibrating active load reduces the effect of noise and threshold nonuniformities of the semiconductor devices (202, 203, 204, 205) used in the read-out amplifier circuitry.

Growing community of inventors

Goleta, CA, United States of America

John A Stineman