| 摘要 |
PURPOSE:To obtain an optical receiving circuit which consists of a small number of circuit components, uses no differentiating circuit, and is tolerant of noise by composing the optical receiving circuit of a photoelectric converting element, a current voltage converting circuit, an AC amplifying circuit, a waveform shaping circuit, and an output buffer circuit. CONSTITUTION:The current voltage converting circuit A converts variation of a photocurrent DELTAI into variation of a voltage and its output voltage (d) is the value obtained by multiplying the photocurrent DELTAI by R1. Then, it is supplied to the AC amplifying circuit B through a coupling capacitor C2. This circuit is an inverter as a digital circuit element and its input and output are cut off by the capacitor in terms of DC. There is almost no current flowing in and out of the input of the inverter and currents flowing in and out of the output of the inverter pass through R4, but their algebraic sum is zero, so an input Vin and an output Vout are invariably equal in means value. Then, the waveform shaping circuit C is constituted as a Schmitt trigger circuit by connecting two inverters in series and connecting the input and output together across a resistance. Therefore, even when an input signal is fine, it is amplified in three stages and its amplitude is above 1.5V without fail, so that the signal is coded into a binary signal correctly by the waveform shaping circuit. |
