I have at least 2 amplifiers in which I can't adjust IDQ to 280 mA. On my initial bias I set Vg1/Vg2 = -2 Volts and Vd= 5V. As I increase Vg1/Vg2 to around -.25 V, Id ~120 mA . I’m afraid to bring Vg any more positive without burning out the parts. With my first assembly I was able to reach Id= 280 mA with Vg1/Vg2= -.67 volts. Id=Id1+Id2+Id3+Id4 and Vg1 and Vg2 are connected together.
I measured the resistance to ground of Vd1, Vd2, Vd3 and Vd4 are 28, 10, 4.2 and 4.2 ohms respectively. The resistance to ground of Vgg1 and Vgg2 are 4.9 and 4.7 mohm respectively
Any insight as to what the problem may be would be appreciated.
