| 摘要 |
A photoresponsive device employing a silicon photocell to excite on illumination of the photocell a transistor in a discriminator circuit and drive the transistor from a non-conducting to a conducting condition. The photovoltaic output of the silicon cell is added to the potential of the direct current potential of a bias source to exceed the threshold conduction potential of the discriminator transistor. Thermostability is achieved by employing a transistor in the bias source of identical type and similar characteristics to the discriminator transistor. The discriminator transistor has an emitter-collector circuit which includes a load resistor, and the output which is developed across the load resistor is amplified by a common emitter transistor amplifier circuit. The transistor of the amplifier circuit is a N-P-N, while the transistor of the discriminator circuit is a P-N-P type. A switching transistor is used in the common emitter circuit of the discriminator transistor. In the optical encoder disclosed, a separate discriminator circuit is employed for each silicon photodiode, but a single direct current bias source is employed. The switching transistors are pulsed, either sequentially or at the same time to interrogate the photodiodes.
|
