| 摘要 |
PURPOSE:To improve carrier wave/noise ratio(CNR) of a transmission signal while reducing the equivalent input noise current of a preamplifier by matching a photo diode and a initial stage amplifier in the required band. CONSTITUTION:In a preamplifier 1, a matching circuit 14 is inserted between a photo diode 11 and an initial stage amplifier 15. A channel select circuit 3 selects the required signal, matching the photo diode 11 and the initial stage amplifier 15 in the required band while adjusting the matching circuit 14. Thus, the equivalent input noise current of the preamplifier 1 can be reduced, resulting in improving the CNR of a transmission signal. |
