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  1. audioguru2

    Need substitute of ICL8038

    The EXAR XR2206 function generator IC might still be available. It has the same functions and frequencies as the ICL8038. The MAX038 is not made anymore.
  2. audioguru2

    Salt-taster

    Hi Walid, It takes a higher current to develop voltage across 470 ohms than it does if R1 is removed and instead 230k is there. Without R1 then the circuit would detect a very weak salt solution. Without R1, the first opamp would amplify the voltage developed across the 220k resistor caused by...
  3. audioguru2

    white led

    5 pages ago, your circuit had 30uF for its supply filter. The max voltage is 370VDC so two 1/2W resistors in series should not arc. If their value each is 100k then they won't get too hot and they will be nearly completely discharged in (30uF x 100k) x 5= 15 seconds. Actually, the LEDs would...
  4. audioguru2

    E.C.G. Schematic

    Did you connect the ECG circuit through a 100 ohm resistor in series with a 4.7uF non-polar coupling capacitor (or two 10uF polarized elactrolytics back-to-back) to the microphone input on your sound card? The resistor stops the last opamp from oscillating when it is driving the capacitance of a...
  5. audioguru2

    LM338/LM318 Not enough power. Vref drops!

    The case must be in very good contact with the heaksink. The electrical connection can be made with a solder terminal bolted to the case. After the voltage dropped, the amount of heat was (10.65V - 4V) x 2.4A= 16W. If the IC was fastened properly to a finned heatsink rated at 4 degrees temp rise...
  6. audioguru2

    need Megaphone circuit?

    A megaphone is a re-entrant horn loudspeaker at one end, a microphone at the other end and a 3W to 15W amplifier in between. They are very loud and are used by a person talking to a crowd of people. The re-entrant horn loudspeaker is very efficient from 500Hz to 4kHz and sounds horrible. 70W to...
  7. audioguru2

    Help Plz - Room Noise Detector

    Look at electret mics in Google and you will learn that they produce an audio signal of from 5mV when the sounds are soft to 100mV when the sounds are loud. Your simulator has a signal generator that can be used instead of a mic. It is a switch with two sections and four positions. The 1st...
  8. audioguru2

    transistor off

    Another guy in your class recently asked for help to make a headphones amplifier that uses a Mosfet. He actually tried to make it by himself before asking for help. Why don't you give the circuit design a try then we can make siggestions to make it better.
  9. audioguru2

    Question for Electrician or Some1 that knows

    If the supply is DC, then maybe the stupid installer connected the polarity backwards.
  10. audioguru2

    transistor off

    No spec's?? Voltage gain. Distortion. Max output level. It is very difficult to make a one-transistor amplifier for stereo. The transistor's part number doesn't matter. A BC547 is the same as a 2N3904 (except the pins are reversed), and a BDxxx is the same as a TIP31. If the supply voltage is...
  11. audioguru2

    Class A amplifier Formulae help!!!

    Of course properly designed transistor amplifiers can have low distortion. They have negative feedback to reduce the distortion. The opamp with only 0.00008% distortion has transistors with plenty of negative feedback. The circuit I simulated has a very low impedance voltage source as its input...
  12. audioguru2

    Class A amplifier Formulae help!!!

    40% distortion or more never sounds good. Modern audio opamps have much lower distortion.
  13. audioguru2

    A very Urgent Question

    The IR detector is tuned to about 40kHz and doesn't work if the IR is steady. The IR must be modulated at the same frequency as the IR receiver IC is tuned to.
  14. audioguru2

    Class A amplifier Formulae help!!!

    The transistor doesn't make much difference. A transistor without negative feedback and a low impedance voltage input signal produces a very distorted output signal when the output level is high. Because the base voltage change does not produce a linear collector current change. It is exponential.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Good, it works. Trimpots can be added in series with the voltage and current setting pots to reduce their max outputs to 30.0V and 3.0A. Then the trimpots can be measured and fixed resistors can be installed. The max operating current of the OPA445AP opamp is only 4.7mA x 46V=216mw. Its load is...
  16. audioguru2

    Build your own jukebox

    My son bought a used laptop pc from E-Bay. Its was owned by a DJ and its hard drive was filled with MP3's. I copied them all to my pc and to the hard drive of an MP3 player I fixed.
  17. audioguru2

    PH meter

    Digikey has thousands of LM4040 2.5V reference ICs in stock. In different packages and from different manufacturers. Enter LM4040 in a search then enter 2.5V. Didn't you see the entire pH meter project on the datasheet for the LMC6001 IC? It tells you all about pH and why R1 is a temperature...
  18. audioguru2

    High Power LED Mood Lamp

    Hi Ante, The absolute max output current allowed for a PIC is only 25mA. The absolute max output current allowed for a 74HCxx is also only 25ma. I think a PIC has the same Mosfets as 74HCxx ICs. My graph of output currents for 74HCxx ICs shows that with a 4.5V supply and a transistor's base...
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    Subodhthok, It is a simple circuit with opamps and transistors. When you learn about opamps and transistors then you will understand the function of each and every component. The Articles section of this website has tutorials on opamps and transistors. Fluffy, My recommended parts list for this...
  20. audioguru2

    PH meter

    Digikey and Newark would have the parts. 1) The opamps are Cmos from National Semiconductor. 2) The "diode" is actually a 2.5V voltage reference IC that is much better than a zener diode. 3) The resistors have 1% values.
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