| 摘要 |
A precision voltage and current source for use, for example, in a transceiver for a carrier-sense multiple access communications network using collision detection wherein the use of one or more precise threshold voltages is required. The threshold voltage(s) is (are) created by a current source which pulls a current through a precise resistive load to yield a precise voltage. A power supply with regulated voltage drives the current source. A feedback voltage from the current source, proportional to the output current of the source, is compared with a reference zener diode voltage; the difference, or error, voltage controls the regulator to drive the regulated power supply voltage in the direction which drives the error voltage to zero. The precise resistive load is preferably formed of two resistors in series. A first threshold voltage is developed across one resistor, corresponding to the average signal level required for receiving signals on the network. A second threshold voltage is developed across the series pair of resistors, corresponding to the minimum average signal level which would be produced by a collision.
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