Apparatus for generating pulse-like constant current having variable

Abstract

An apparatus for generating a pulse-like constant current with a variable pulse width for use in evaluating thermal characteristics of a laser diode. The apparatus comprises a first constant current (or voltage) circuit constituted by a high-speed amplifer, a second constant (or voltage) circuit constituted by a low-speed amplifier and connected in parallel with the first constant current circuit, a bias circuit for increasing higher the output voltage of the second constant current circuit than that of the first constant current circuit, a switching circuit for turning on and off the first and second constant current circuits in response to first and second timing signals, respectively, in such a manner that the first timing signal and the second timing signal are simultaneously turned on while the second timing signal is turned off only after the first timing signal has been turned off, and a regulator for changing the width of the output current pulse by varying the on/off durations of the first and second timing signals. For evaluating the thermal characteristics of the laser diode, the pulse-like constant current is applied for excitation and the pulse width of the current is varied to change the light emission characteristics of the diodes, which are measured and compared for making evaluation.