| 摘要 |
A voltage reference source for supplying one or more reference voltages to load circuitry. The reference source comprises an ungrounded voltage reference cell (20) floated between two power supply levels (Vcc and Vee), and an operational amplifier (22) whose non-inverting input (terminal 9) may be connected to sense the voltage of the load circuit's ground node. The inverting input of the op amp (terminal 10) may be connected to various nodes (6, 8, 11) in the reference cell; the voltage on the selected node is forced to match the sensed ground voltage and that node thus becomes an internal ground reference point. The high input impedance of the op amp (22) limits the current in the ground sensing path to a very low value, such as about 10 nA. Consequently, very little voltage is developed in the leads from the load circuit's ground node to the op amp input. The floating reference cell (20) has a resistive divider (48, 50) across its output. The various nodes along the resistive divider are the nodes selectable as the internal ground node. A variety of voltages of both positive and negative polarity may be derived from the zener diode reference. One or more buffer amplifiers may be connected either to the output of the reference cell or to points on the voltage divider, to provide buffered full Kelvin "force-sense" outputs.
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