| 摘要 |
A driver circuit for controlling a laser diode in response to a digital input signal, said driver circuit includes: a switching circuit (18, 24) for receiving a digital input signal (14) having a high voltage level and a low voltage level, said switching circuit, in operation, generating a switching output comprising a first switching voltage level in response to the high voltage level and a second switching voltage level responsive to the low voltage level. An emitter follower (36) has as its input the switching output for generating an emitter follower output comprising a first follower output voltage level in response to the first switching voltage level and a second follower output voltage level in response to the second switching voltage leve. A VMOS field effect transistor (42) has a gate connected to said emitter follower (36) so that, in operation, the voltage level at the gate is substantially equal to the voltage level of the output of the emitter follower, and has a source biased to a pre-selected source voltage. The VMOS field effect transistor (42) is in operation, enabled whenever the voltage level at the gate is substantially greater than the source voltage, and disabled when the voltage level at the gate is not substantially greater than the source voltage, one of the first and second follower output voltage levels being substantially greater than the source voltage and the other of said follower output voltage levels being no greater than a voltage level near the source voltage. A laser diode (12) is connected in series with the VMOS field effect transistor for emitting light whenever the VMOS field effect transistor is enabled. |
