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  1. audioguru2

    IR Audio Receiver

    All transistors in your circuit are emitter-followers that have no voltage gain. Then the signal level is extremely weak. You need an amplifier circuit. The piezo transducer is a capacitor that does not conduct DC so a load resistor is needed for the transistors. One transistor is not needed.
  2. audioguru2

    0-30V Stabilized Power Supply

    The single 2N3055 transistor in the original project got too hot (dissipating 89W) when the output voltage was low or was shorted and the current was set to 3A. The modified and corrected circuit has a higher transformer voltage which causes even more heat so two 2N3055 transistors are used to...
  3. audioguru2

    SAW duplexer/SAW filter

    You will find answers in Google.
  4. audioguru2

    room noise detector

    You forgot to provide a link to our Room Noise Detector project: http://www.electronics-lab.com/projects/sensors/012/index.html It has a switch to select which sound level causes its LED to light. How can a single LED show three different sound levels? EDIT: An RGB 3-colours LED?
  5. audioguru2

    How to use a BJT as a switch..

    The very old circuit already had its extremely old opamp changed to a 741 opamp. The first opamp needed C3 but the 741 opamp does not need C3. I would use inexpensive, low noise and wide bandwidth TL071 opamps in this project.
  6. audioguru2

    0-30V Stabilized Power Supply

    Your power supply will have a maximum regulated output of about 25VDC because the voltage from your transformer is too low for 30VDC. You should modify the voltage setting pot so that it cannot be adjusted higher than about 25VDC where the output will be full of ripple.
  7. audioguru2

    cordless phone

    An electric car? ;D
  8. audioguru2

    0-30V Stabilized Power Supply

    The circuit in this thread makes 0V to 30VDC at 3A. It uses a 28VAC transformer. Yours will be different since your transformer's voltage is too low. It will provide a max output current of 5A if you use 3 output transistors (each with a 0.33 ohm emitter resistor) and change R7 to 0.27 ohms/10W...
  9. audioguru2

    Soft Power Up?

    If you switch its positive supply then an NPN emitter-follower can provide a slowly ramping positive supply to the Jfets.
  10. audioguru2

    Soft Power Up?

    Since you are switching its ground instead of switching its positive supply to turn it on and off then ramping the power supply voltage must also be done backwards. A PNP emitter-follower transistor can provide the Jfet preamp with a ramping 0V.
  11. audioguru2

    0-30V Stabilized Power Supply

    The rectifier bridge will have a voltage loss of about 2V. The current-sensing resistor R7 uses 1.4V at 3A. The output transistor has a max voltage loss of about 2V. The driver transistor has a max voltage loss of about 1V. The opamp U2 has a max voltage loss of about 2V. The main filter...
  12. audioguru2

    Soft Power Up?

    The Jfet is self-biased so its output suddenly jumps up when its power supply voltage is applied. If you slowly ramp up its power supply voltage then it should not make a POP sound.
  13. audioguru2

    Soft Power Up?

    Post its schematic for us to see if its biasing can have a slow ramp-up.
  14. audioguru2

    0-30V Stabilized Power Supply

    The voltage from your 24VAC transformer will allow the project to have a regulated max 25VDC output if the main filter capacitor has a high value. Add more output transistors and driver transistors for more Amps. The value of R7 determines the max adjustable Amps. If your transformer has two...
  15. audioguru2

    how to test a condenser mic

    A condenser mic needs a 48V power supply. An electret mic is similar but has a 48V charge built-in. The electret mic has a FET transistor impedance converter that must be powered by about 0.5mA from a resistor connected to a few volts. The output level is about 10mV if you talk in a normal...
  16. audioguru2

    A SERIOUS PROBLEM

    It will probably work properly if you use the specified 74HC299 IC.
  17. audioguru2

    How to use a BJT as a switch..

    Yes. TR1 will turn on and it will turn on the alarm circuit.
  18. audioguru2

    Attack site

    My son gave me RAM for Father's Day. Now I have 3 times as much RAM as I had and my pc runs much quicker. Now the anti-virus program can scan and I don't notice. It has caught many viruses before they are opened and has deleted or quarantined them. Never has a virus been found too late during a...
  19. audioguru2

    uestion about the operation of photodiode

    Yes. But since its area is very small then its generated current is also very small.
  20. audioguru2

    Attack site

    My Norton anti-virus software updates itself daily and catches viruses before they are active on my pc. I surf many other sites without any of the problems I have with accessing Electronic-Lab.
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