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  1. audioguru2

    Additional Information

    Hi Naveed's team leader, You don't need to write a specification for the simple circuit of the Dancing LEDs project. Its operation depends entirely on the amount of sound level picked-up by its microphone. The sound level is determined by its power, closeness to the microphone and room...
  2. audioguru2

    Additional Information

    Hi Naveed, You can't read the way Europeans write component values? They use the multiplier letter instead of the decimal point. R1 and R2 are 4.7K R5 is a 2.2M trimpot R12 and R16 are 56 ohms. The author's new website shows C1 as 1uF and C2 as 100uF.
  3. audioguru2

    Lie Detctor

    Hi Cody, The transistor isn't working or the batteries aren't 4.5V. The schematic shows a longer line for the positive terminal of each battery cell. Each of the two batteries are 3 cells and they could be AA cells. With nothing connected to the electrodes the meter should try to go backwards...
  4. audioguru2

    fm tranismiter

    Hi Alun, You can't get 100MHz? The only other RF thingy I made was another FM transmitter in about 1968, it used a germanium transistor and worked just fine. Nope, I just remembered that around that time I was also fooling around with a tunnel diode transmitter. A wire broke off the tunnel diode...
  5. audioguru2

    tranasistor with amplifying factor 200

    Hi Kevin, The device to cancel the non-linearity of a transistor is called a differential stage, negative feedback, or an AC-coupled diode circuit like I recently posted in our Therory forum: http://www.electronics-lab.com/forum/index.php?topic=3057.0
  6. audioguru2

    tranasistor with amplifying factor 200

    Kevin, In addition to a transistor's beta not being constant with collector current and temperature changes, as shown on the datasheets, its transconductance is also non-linear. That is why differential transistor circuits are used as the input stages of audio amplifiers and oscilloscopes, so...
  7. audioguru2

    Setup Reversal

    Hi South Bank, Welcome to our forum.  ;D You don't say anything about voltage or current. You also don't say whether your battery cells are completely separate or are two in series. If the battery cells are 3.6V lithium, or lower-voltage types in series, for low load and charging currents I...
  8. audioguru2

    PCM Speech CODEC

    Hi Clueless, Switched capacitor filter ICs use a "non-overlapping clock generator". I don't know how to make one easily using a Johnson Counter like a CD4018, maybe it needs two cascaded CD4018 counters. Please post your Johnson Counter defective bi-phase clock circuit so we can troubleshoot it.
  9. audioguru2

    Electronic Stethoscope

    Hi Bugzy, Welcome to our forum.  ;D Are you making the original Electronic Stethoscope project or the corrected and improved Electronic Stethoscope-2 project? Most electret microphones have very good frequency response of from about 30Hz to about 15KHz and the response is fairly flat. Whoever...
  10. audioguru2

    ...about the 25W MOSFET(or HEXFET) amp...again...

    Hi Sasi, You have a good idea to use a coil at the output to isolate capacitive loads. R14 and R15 should be deleted since they cause severe crossover distortion.  :o
  11. audioguru2

    fm tranismiter

    Hi Alun, The 2N3904 transistors that I used have half the output capacitance of your 2N2222A.  ;D
  12. audioguru2

    Charging Battery !

    Hi Spike, Please don't make 2 new topics for the same battery charger request. I posted some battery charger precautions and a circuit in your 2nd topic. The only difference I could find between a Lithium-Ion charger abd a Lithium-Poymer charger is that the polymer battery must be charged...
  13. audioguru2

    Charging Battery !

    Hi Spike, Welcome to our forum. Charging a lithium battery presents a severe fire hazzard if the charging is incorrect or if the charger fails. I suggest that you look at your battery manufacturer's website for their recommendations. We have many articles in our Articles section, and its link...
  14. audioguru2

    fm tranismiter

    Hi Alun, I don't know why your oscillator's frequency is so high. My FM transmitter can be tuned below the FM band, how far below I can't measure. You would expect your 39pF cap to work well at VHF due to its small value. Try another transistor. Maybe the one you are using has unusually low...
  15. audioguru2

    tranasistor with amplifying factor 200

    I am sorry but that is not true, Kevin. In the BC547C example transistor that I posted above, its max collector current is 100mA. If you bias it so that its collector current is half of max, its beta is extremely unlinear. When it is fully conducting 100mA, its beta is typically about 115 from...
  16. audioguru2

    PCM Speech CODEC

    Hi Clueless, Welcome to our forum. Aren't you allowed to use a switched-capacitor filter IC?
  17. audioguru2

    Buried wire detector

    Hi Kiwi, Your LM351 opamp isn't made anymore, so full details about it are no longer available. Its datasheet shows it with a minimum of 10V for its supply voltage, but its text says that it will perform with reduced spec's with a supply voltage as low as 8V. I suggest using a more modern opamp...
  18. audioguru2

    tranasistor with amplifying factor 200

    Hi Ssuet, Welcome to our forum.  ;D You can't purchase a transistor with a beta of exactly 200. Their beta come in a range of values for a particular transistor. You can pay more for a BC547B, where the manufacurer has tested and selected a narrow range of beta from 200 to 450, but it changes...
  19. audioguru2

    complimentary symmetry amplifier

    Hi Kevin, Your article shows a variation of a vacuum tube amplifier called, "Push-Pull". It uses driver and output transformers and was used in transistor radios in the 60's. Audio amps and opamps that use bipolar transistors don't have any voltage gain in their Complementary-Symmetry...
  20. audioguru2

    ...about the 25W MOSFET(or HEXFET) amp...again...

    Hi again Sasi, I nearly forgot. With a total of 66V for a supply, bipolar or darlington output transistors wouldn't have the huge voltage loss of the Mosfet-followers, so the output power would be much more than only 25W and the output transistors and power supply would fail due to too much...
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