| 摘要 |
<p>A Safe Operating Area (SOA) circuit is constructed including a synthetic large value resistor that is an active current source whose output current is related to the power supply voltage, and whose absolute value may be arbitrarily low. A piece-wise current source is provided which includes means for generating one or more control voltages in order to control the level of output current in response to the input voltage. In one embodiment, each of the control signal means includes feedback means and a summing node, so that one or more functions are performed using a control signal as an input, with the result fed back to the summing node. In this manner, a complex function can easily be provided for controlling the magnitude of the output current. In one embodiment, the one or more control signals are provided by one or more saturating current mirrors in order to limit the output current made available. The saturating current mirror comprises a bipolar transistor having a plurality of collectors, one of the collectors serving to provide the output current, and one or more collectors connected to circuit elements which have current characteristics with respect to the input voltage. In another embodiment, the bipolar transistor having a plurality of collectors is replaced by a plurality of MOS transistors, having channel widths of desired ratios in order to provide a desired transfer function. <IMAGE></p> |
