![]() ![]() Hey CrossRoads i was about to implement the circuit you were going to use, I see how you state that it is easier to pull the current into the coils rather than push the current into it by placing it at the emitter. ![]() Would a Heat-sink be needed for this BJT also, since it is passing a big gain in current? Should i include a priming BJT to the Darlington and then retest the circuit?Īdditional thoughts: The Additional BJT will be powered by 15 volts at the collector. 1956/.02 = 9.78 A/A I'm assuming this is when the gain starts failing because of the limitations of the op-amp to output a max of 20 mA, because we expect about 600 to be the gain when operating correctly. Re = 23 ohms, So this is when the darling ton begins to fail. I started with 44 ohms and worked my way down to 23 ohms. I applied a control voltage to the op-amp non-inverting terminal, then i measured the Voltage at the Emitter while varying this resistance. Hey So i followed Rugged Circuits Method of dropping the resistance until i see a a drop in Voltage at the emitter Is there any method to increase this voltage up to about 12 volts? I have supplied the datasheet of the transistor, and a copy of the imageĭata Sheet: Intelligent Power and Sensing Technologies | onsemi I believe that there must be something in the data sheet of the Darlington i must not understand that is giving me such a huge voltage drop. The voltage drops from 12 volts all the way down to 1.4 volts. However, when i connect the VE to alternator coils, which i measured to be about 4 ohms. When there is no Load attached to the emitter, this is exactly what happens. What the expected behavior of the circuit is suppose to be is that when i apply a control voltage(Vc) to pin 12, the collector to base voltage(Vcb) will drop the required amount of voltage so that the voltage at the emitter(Ve) will be the same as the control voltage.įor example if i applied 12 volts to VC, i should expect that the Vcb will drop 3 volts so that VE will equal 12 volts. ![]() Seen in the bottom picture is the schematic I am testing.The op amp is powered with +/- 15 volts and the collector of the Darlington is powered by 15 volts also. I'm trying to figure out an issue I have with a Darlington Transistor. ![]()
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