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  1. audioguru2

    Voltage Regulator Question

    Your choice of a low-dropout regulator that won't tolerate a ceramic output capacitor and your QT301 ICs that need a ceramic supply cap cause a conflict because they are not compatable. 
  2. audioguru2

    Simple O2 meter with LM3915

    R5 in this DIY circuit is 10k. Up to 20 LEDs will have their current flowing through it so its value is way too high. Maybe it should be 10 ohms. The circuit needs supply bypass caps as per the datasheet. The value of R3 should be the same as R1. Maybe the values for R3 and R4 are swapped. I...
  3. audioguru2

    Voltage Regulator Question

    I think the "engineers" at the regulator manufacturer are thinking about ordinary regulators, not low-dropout ones. An ordinary regulator uses a ceramic cap for high frequency suppresion. If you completely suppress high frequencies at the output of an older low dropout regulator then it will...
  4. audioguru2

    High screech sound over telephone?

    A telephone doesn't produce a loud sound. A telephone line doesn't pass high pitched sound above about 3kHz. I measured phone lines that were flat to about only 800Hz and down 14dB at 3kHz. The phone company showed me that it met their spec's. -7.5dB at 3kHz one-way into their equipment is their...
  5. audioguru2

    Voltage Regulator Question

    The March, 2005 datasheet of the LE00 low-dropout regulator is pretty new and says the ICs should have a bypass capacitor with an ESR from 0.1 to 10 ohms. Every schematic shown has a polarized output bypass capacitor. Ceramic caps have an ESR much lower, and are not polarized. Try a ceramic...
  6. audioguru2

    What are Heat Sinks??

    150 degrees C is pretty darn hot! My computer's Pentium4 2.93GHz processor has a heatsink with a variable-speed fan on it. Intel's program shows me the internal temperature of the processor is usually only 52 degrees C and the fan speeds up to keep that temp when the processor is thinking very hard.
  7. audioguru2

    Multicolor fading leds

    If you want only one set of LEDs to be lighted at a time, then only one fading opamp circuit is needed. Then it can be connected to each output transistor in sequence with CD4066 analog gates that are turned on by the chaser circuit.
  8. audioguru2

    Simple O2 meter with LM3915

    Hi Wellington. ;D Might be caused by other problems. The schematic has the definitions for pins 6 and 8 of the LM3914's backwards. D1 and D6 are correct on the schematic. 30V zeners don't conduct with an input of only 9V so they must be the wrong voltage. I have never seen a zener with such a...
  9. audioguru2

    Another INVERTER we can talk about..

    Your circuit has a positive voltage shift and very high resistor values. Mosfets need their inputs to be zero volts when off and low resistance values to switch quickly. Use a counter with gates instead of resistors to make the signals that feed the Mosfets.
  10. audioguru2

    RF power amp 3.5 mhz 150w

    This RF amplifier is tuned to 3.5MHz. The FM broadcast band has frequencies 28 times higher at around 100MHz. Operating a radio transmitter at these frequencies with such high power is highly illegal anyway.
  11. audioguru2

    Another INVERTER we can talk about..

    Your circuit and Sasi's circuit are completely different. Sasi's circuit appears to be a square-wave inverter with a very small "dead-time". Your circuit needs a way to drive output Mosfets.
  12. audioguru2

    Stereo Audio power amplifier 2 x 40W - 80W

    Good, it works well. ;D
  13. audioguru2

    Multicolor fading leds

    Now you need to make a chaser circuit with an oscillator and a CD4017 sequenceing IC. Then you need some kind of gating for the transistors that drive the LEDs to turn them off by the chaser.
  14. audioguru2

    Stereo Audio power amplifier 2 x 40W - 80W

    Does the microphone pickup music? Does the amplifier also have an input selector switch and a line-level input for music that needs a shielded audio cable? When the pot is turned down, the power amp shouldn't have an input. Maybe the pot is defective and doesn't go down to zero. A higher...
  15. audioguru2

    Voltage Regulator Question

    The datasheet for the regulator shows the safe range of an output capacitor's ESR. Ceramic caps have an ESR much too low for them which would cause high frequency oscillation. We are talking only about capacitors from the output of a low dropout regulator to ground.
  16. audioguru2

    High screech sound over telephone?

    The sound is caused by acoustical feedback. The handset has a microphone and a little ear-speaker. The phone amplifies the microphone's signal and gives a little to the ear-speaker so you can hear how loud you are speaking, called "sidetone". You make a sound coupler with your hands to feed...
  17. audioguru2

    Multicolor fading leds

    Since it would be complicated to switch fading LEDs and you are a noobie, why not just make the fading portion of your circuit now. Then make it switch from LED to LED later.
  18. audioguru2

    Multicolor fading leds

    The circuit I posted slowly brightens and fades the LEDs. What and why do you want to switch? Do you want the "satellites" to turn on in sequence like in a chaser? Then you have satellite #1 brighten and fade then turn off while satellite #2 brightens and fades then turns off while satellite #3...
  19. audioguru2

    0-30V PSU - prblem with current limiter

    Hi Mikevein, Welcome to our forum. ;D If the negative 5.6V supply doesn't work then Q1 will turn on and cause U2 to get hot. Also the current regulator U3 won't work. Check that you have -5.6V across D7. Make sure that you have the substitute transistors wired correctly. If they have the...
  20. audioguru2

    Voltage Regulator Question

    On the datasheet for the low-dropout regulator you selected, there is a listing of the allowable ESR of the output cap. A ceramic cap has an ESR much too low and will cause the regulator to oscillate unless a low value resistor is added in series with it. Even additional ceramic caps on the...
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