i made an electronic load for 150 watt photovoltaic panel . i can control the circuit but the measured voltage by the voltmeter isn't the real volt relevant to the current , for example i got 3 amp it should give 30 volt on the drain ( where the +ve terminal of the panel is connected ) but the voltmeter reads 27 volt , where did this loss go ? , i used four IRF530 but they are from the same manufacturer ( they have different numbers on it) but i don't think that this is the problem . this is the circuit without using 10 KΩ in feedbackhttp://forum.allaboutcircuits.com/attachment.php?attachmentid=62147&d=1385954290