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  1. audioguru2

    transistor off

    Your new output stage looks good. But: 1) It has a very high output impedance. It should have a low output impedance. 2) It doesn't have a method to automatically adjust the gate voltage for the Mosfet. 3) It wastes 3W as heat.
  2. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    Hi Kachew, If your inverter will have a max load of 150W then its total power including heating is 188W. The average current from the 12V battery is 188/12= 15.7A but the peak current is 2-root-2 times= 44.4A because it has a modified sine-wave with pauses. The IRF540 Mosfet is pretty old and...
  3. audioguru2

    High Power LED Mood Lamp

    Hi Harald, Welcome to our forum. The author of out Mood Lamp project used a heatsink on the first one he made and it is shown on his website. But for our project he says you can use a heatsink if you want. The 10k base resistors have a value that is way too high for the transistors to conduct...
  4. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    These are switching inverters that do not have a linear amplifier. They don't have negative feedback. They switch 12VAC at a very high current into the low voltage winding of a transformer and the transformer steps-up the voltage. They work fine and are not unstable.
  5. audioguru2

    Lowpass filter for subwoofer

    Pick a capacitor type, any capacitor type. The 39pf capacitor is a ceramic, not an old silver mica.
  6. audioguru2

    Microwave Transformer

    Its high voltage winding is about 2000V at 375mA which is more than enough to kill you.
  7. audioguru2

    Lowpass filter for subwoofer

    I have seen many 39pF ceramic capacitors, but never a tantalum capacitor with such a low value.
  8. audioguru2

    Lowpass filter for subwoofer

    Please do not make duplicate posts. I answerered your questions about our Lowpass Filter for Subwoofer project in your other post. The parts list and schematic in the project are still wrong. The parts layout and picture are correct. The LED is shown connected backwards on the parts layout.
  9. audioguru2

    transistor off

    hi Elix, Your new current regulator looks like it will pull the drain of the Mosfet to ground. I have fixed it and show another one. Please start again: 1) Your opamp is the wrong one (it oscillates at low gain). Its circuit has a high signal loss. The opamp does nothing good in your circuit...
  10. audioguru2

    Lowpass filter for subwoofer

    Hi Collin, Many people are confused with the errors in this project. It is too bad nobody fixed the mistakes in the parts list and on the schematic. The parts layout drawing is correct except the LED is shown backwards. Look at the picture. It clearly shows ceramic capacitors and metallized...
  11. audioguru2

    Two PCBs off of one power source

    Bruce, Each circuit has its own output amplifier to drive a speaker. You cannot short the outputs together to drive a single speaker. Use a separate speaker for each circuit. I suggested adding resistors in series with the output of each one to isolate them from each other. The resistors become...
  12. audioguru2

    transistor off

    The Mosfet is saturated and the output swing measures in micro-volts. The current regulator is not working because it is connected wrong. Here is the current regulator from the LM317 datasheet:
  13. audioguru2

    transistor off

    Don't use an OP37 opamp because it is unstable when it has low gain. Use an "ordinary" opamp that is stable at any amount of gain. Your opamp has a "gain" much less than a piece of wire. Its gain is only 0.033. A single or a split supply has nothing to do with it. The OP37 is made for high gain...
  14. audioguru2

    Two PCBs off of one power source

    Two circuits cannot share the same speaker. They will get damaged. The circuits feed a mixer circuit then the mixer circuit feeds a power amplifier circuit that drives a single speaker. You can make a mixer circuit with 2 resistors. There are a few low-power power amplifier ICs that work with a...
  15. audioguru2

    Two PCBs off of one power source

    Of course they can operate from the same battery power supply. But it sounds like you are shorting their outputs together that will damage one or both of them. You should never short outputs of circuits together, even if one of them is turned off. Add a mixer circuit for both circuits to feed...
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    You don't need fine-tuning controls on a variable power supply.
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    I showed trimpots with three terminals but wired for two terminals, connected in series with pots that have three separate terminals. Nothing is in parallel. The series trimpots reduce the max voltages.
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    I don't recommend using two pots in series for fine and coarse control. I recommend adding trimpots or fixed resistors in series with the existing pots to reduce the max voltage to exactly 30.0V and to reduce the max current to exactly 3.0A. All 3 terminals should always be used on pots. Then...
  19. audioguru2

    white led

    The datasheets for Limileds say to drive them with a current regulator. If their total voltage is 7V or less (you must measure it because it could be 3V or up to 4V each) then a 7808 (measure it too) with a current-limiting resistor will feed them 335ma. A 78xx as a current regulator gets very...
  20. audioguru2

    transistor off

    Your OP37A opamp has a voltage gain of 19k/10k= 1.9 with a low impedance source, and a voltage gain of 19k/(4.7k + 10k)= 1.3 without an input. But the OP37A opamp is de-compensated and is unstable with a voltage gain of less than 5. It will oscillate. I don't think the 150pF capacitor at the...
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