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  1. audioguru2

    Linear Voltage Regulator Design

    Hi Cyw, You didn't finish your circuit with the important stuff I mentioned, so I added/changed a few things. About the only thing that remains is adding current limiting or regulation. If you draw too much current or short the output, it will blow-up! ;D
  2. audioguru2

    Voltage control oscillator VCO

    Hi Walid, I am sorry but I am not going to analyse and calculate my FM transmitter circuit. I designed it by using experience, and from copying others. If you look on the web you will find hundreds of FM transmitter circuits, and they all use the same tuned circuits and many of the entire...
  3. audioguru2

    BENCH POWER SUPPLY

    The LED's wires are completely separate from the switch. Why not leave it that way? Use the switch contacts to switch both wires of the mains to the transformer, and connect the LED through a suitable current-limiting resistor to the DC in the circuit. Then when you turn-on the switch, the...
  4. audioguru2

    Linear Voltage Regulator Design

    Hi Alun, An old LM358 is half an old LM324. They are about the 1st low-power opamps ever made so sure they are darn slow. They slew 2.5V in 5us which is only 0.5V/us. Their output is slew-rate limited above only 5kHz. :'( Your P-channel Mosfet in a low-dropout regulator is a good idea to keep...
  5. audioguru2

    Voltage control oscillator VCO

    It isn't built yet but its freq. calculates too high. Yeah, the error in the maths will be cancelled by stray capacitance. ;D
  6. audioguru2

    100 uH coil

    I guess the ferrite core is a Philips one with 6 holes for the wire to loop through and has 5 turns of wire in it. Entering Ferroxcube in Google linked to a site by Ferroxcube. They have a few of these cores and the ones with the highest inductance resonate below 100MHz. Here is a good one:
  7. audioguru2

    Stripboard + Acetone

    Hi Autir, Acetone is nasty, deadly stuff. Why use it? Isopropyl alcohol is full of or absorbs water, doesn't it? Keep away from it. I have used ordinary rosin-core solder for more than 40 years and have never removed flux residue from my very many projects. Many of my projects use high impedance...
  8. audioguru2

    NiCd - NiMH Charger

    i Dito, Welcome to our forum. ;D I don't know what the 0,1 is for, and I don't understand the function of the entire project. It doesn't have anything to prevent the batteries from over-charging! I just use a supply voltage a little higher than the voltage of the fully-charged battery, feed it...
  9. audioguru2

    100 uH coil

    Our 3W FM transmitter project uses a few RF chokes and tells how to make them: http://www.electronics-lab.com/projects/rf/016/index.html One of our 4W FM transmitter projects also uses RF chokes but its translation is difficult to understand.
  10. audioguru2

    Linear Voltage Regulator Design

    An LM358 is very slow, about the same speed as the output transistor. A modern faster opamp would have better transient response. It wouldn't be difficult to compensate it with a little capacitor across the 40k resistor. 40k isn't a standard value so instead I would use 33k in series with a...
  11. audioguru2

    A chock coil

    Without proper test equipment you will be working blindly. Aren't you the guy who wants to be an expert circuit designer? I have never seen a blind expert circuit designer. :( It is fine for you to ask about the details of design, then you will learn from us. ;D
  12. audioguru2

    BENCH POWER SUPPLY

  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    Why? All the parts are needed in the voltage regulator circuit. If you use a DAC to provide a reference voltage, then you don't need the project's zener diode/opamp reference voltage circuit.
  14. audioguru2

    positive and negative voltages

    An LM7912 doesn't make a negative supply, it is not a generator. It just regulates a negative supply that is already there. Its input voltage must be at least -15V for it to work perfectly. ::)
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Cyw, That part of the circuit is more than only the voltage regulator. U2 drives the darlington emitter followers connection of Q2 and Q4 and the ratio of R12/R11 plus 1 is the voltage gain. They have an extremely low output impedance and good voltage regulation because the open-loop gain of...
  16. audioguru2

    BENCH POWER SUPPLY

    Hi Um...Me, Measure the output voltage of the 3V wall adapter. It is rated to give an output of 3.0V only when it has a load of 300mA. But its output voltage isn't regulated and your load draws much less than 300mA, so its output voltage is high enough to light 3.2V white LEDs but not high...
  17. audioguru2

    A chock coil

    Until you are experienced in circuit "gesign" it is advised that you build a "bototype". (He, he.) ;D Then you can tweak parts values in the prototype to make it work as well as it can. In the prototype you will learn that 100MHz is a very high frequency. At such a high frequency, you will learn...
  18. audioguru2

    A chock coil

    With a small coupling cap so it doesn't have any bass, and no pre-emphasis so it doesn't have any treble, then it would sound much worse than an old telephone. 8)
  19. audioguru2

    MIC coupling capacitor

    Hi Walid, It is difficult to calculate the gain and input impedance of the mic preamp you posted because it has negative feedback applied to its input. The transistor has an input impedance of about 2k ohms and the negative feedback of about 2k ohms is in parallel with it. It is fed from a...
  20. audioguru2

    A chock coil

    The circuit's author likes big values. Look at the huge value for the emitter bypass cap. It would still work very well at a frequency 200 times lower.
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