audioguru Posted November 25, 2005 Report Share Posted November 25, 2005 Hi Smit,Your project's U3 and Q3 aren't working properly.Check the pins layout of Q3 and the values of R19 and R20.Q3 should turn on when the output of U3 drops 5V and more below the positive supply voltage.Test Q3 by connecting a 10k resistor from its base to ground and it should turn on.Maybe U3 is busted from having too high a supply voltage. Since its output is 34V then its positive supply must be about 35.5V, plus its negative supply of -5.6V equals a total supply for it of 41.1V. If it is a TL081 then its spec'd absolute max supply voltage is only 36V.U2 has the same high supply voltage problem.That's why I recommend using ICs that have a higher supply voltage rating in this project.What is your project's positive supply voltage without a load? If it is low enough when added to the negative supply voltage then common opamps rated for a 44V supply voltage could be used. ;D Quote Link to comment Share on other sites More sharing options...
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