| 摘要 |
An operational amplifier suitable for inclusion in an integrated circuit device operating as a transceiver at a coaxial media interface to a network meeting IEEE 802.3 standards. To be included in an integrated circuit package the operational amplifier must have low-power consumption and yet generate up to 80 mA of current onto the network. A design method achieves this goal, producing an operational amplifier having three independently-positioned, isolated, poles. A current generator and level shifter is employed with the operational amplifier which generates a current precisely proportional to a "collision" reference voltage, the current is compensated for changes in temperature and for variations in transistor gain (hFE). A very wide band level shifter matches the current generated to the requirements of the operational amplifier so that 10% to 90% changes in current generated by the op amp can occur in 1/2 to 3/4 of a nanosecond, yet the level shifter does not consume much power. The current generator provides a single point of circuit element control for compensating for hFE variation in three transistors used within the current generator. The level shifter employs current-steering to produce the switched current which is exceptionally fast and low in asymmetry. The process used in integrated circuit manufacture permits tight control of the elements within the operational amplifier so that parameters can be held within 2% of the tolerances specified in the IEEE 802.3 standards without need of field "trimming".
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