Abstract: A circuit and method for driving a laser diode with high stability. A steady state current is generated and used to drive the laser diode. A dynamic feedback signal is generated and used to operate the laser diode in a constant power mode. An operational amplifier having a transistor and an RC circuit in the feedback loop is used to couple the drive voltage source to the laser diode. A potentiometer in the inverting amplifier input is used to control the laser diode output current amplitude. A longevity signal is provided to indicate whether or not the laser diode current is excessive.

Abstract: A system and methods for transmitting analog signals, particularly analog signals derived from an optical signal intensity, in a noisy environment over a length of cable. The optical signal is sensed by a photodetector, which is bootstrapped and backbiased to minimize the capacitive effect of the photodetector, and converted to a voltage by a transconductance stage. The voltage signal is then driven over a length of cable by a buffer amplifier having a low impedance output substantially matched to the characteristic impedance of the cable (e.g., twin lead wires having a Z.sub.0 =120), to a second circuit board. The cable length may be, e.g, less than a meter. The second circuit board contains a high gain amplifier stage and circuits for processing the high gain amplifier signal to derive, e.g, a peak pulse amplitude corresponding to the peak intensity of the optical signal sensed at the first circuit board.