High Power Adjustable Load

An adjustable load resistance is indispensable for the realistic testing of power output stages. This circuit provides an electronic alternative to the use of inconvenient high-wattage resistors.The circuit described here has two modes of operation. It can function as an adjustable current sink or as a variable load resistance. At a voltage of between 0 V and a maximum 100 V the sink current can be set in the range 0 A to 20 A. As a load resistance it can be set to values from less than 1 ? to more than 100 k?. The maximum power dissipation is in the region of 100 W. The circuit is designed for operation with DC voltages, but with the addition of a rectifier can also be used with (low frequency) AC voltages. A carefully constructed and calibrated unit can deliver a linearity of better than 0.5 %.