| 摘要 |
PURPOSE:To prevent light-emitting elements from being destroyed due to driving current or the life time thereof being shortened by causing the value of the resistance of a bypass circuit to be changed by combining a plurality of fixed resistors. CONSTITUTION:Resistors R14, R13 and R12, and a capacitor C2 are connected in series in this order, so that any one of a terminal A of resistor R14, a node B of resistor R14 and resistor R13, a node C of resistor R13 and resistor R12 can be connected to the anode of a laser diode 1. With such a construction, when a light emission threshold value current is large and a driving current is small, node A is connected to the anode of the laser diode 1. When a light emission threshold value current is small and a driving current is small, a terminal C is connected to the anode of the laser diode 1. As a result. even if a driving current differs to obtain a predetermined laser output, overshoot can always be suppressed to a minimum, causing no delay to an extent more than required. |
