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  1. audioguru2

    Electronic Stethoscope

    Hi Hakyman, welcome back. ;D You can purchase a cheap wireless link that is made for a wireless mouse and similar stuff. You probably must modify them with bigger coupling capacitors to get very low heart frequencies. It is complicated to make a stable transmitter and receiver.
  2. audioguru2

    n-chanel enhancement mode power mosfet

    Hi Goatman, It's great that you got it working well. The sound barrier is more than 700mph! I like the tie-wrap that holds a wheel on. ;D I see heavy wear on the tires, they'll need replacement soon.
  3. audioguru2

    TRANSISTOR ATTENUATOR?

    A little confusing. In Alun's inverting opamp circuit, if the output is -1V, then the input of the opamp is +1uV and the circuit's input to the 47k resistor is +0.212767V. Due to the opamp's extremely high gain and extemely high input impedance, Rf and Rin simply form a voltage divider to...
  4. audioguru2

    Electric assist bike

    If it can do a wheelie then please post a video! ;D
  5. audioguru2

    Charging 39 NiMH cell battery pack

    My AA size Ni-MH cells measure 1.4V after charging slowly all night. Therefore 39 of them would require a charger output voltage of at least 54.6V plus more volts for the current limiter. A charger for a 48V lead-acid battery would probably have enough volts but the current would be excessive. A...
  6. audioguru2

    Deja-vu, reply to replies

    Hi Ante buddy, Welcome back! ;D
  7. audioguru2

    n-chanel enhancement mode power mosfet

    Well I don't think it would oscillate. This form of gross overdrive causes the signal to sort of fold over on itself. Look at it on a 'scope or listen to it happen. It's weird! :o ;D
  8. audioguru2

    n-chanel enhancement mode power mosfet

    Hi Alun, You are talking about JFET-input opamps and Goatman mentioned common-mode. Did you know about the cool trick that most JFET-input opamps can do? 1) Make an opamp follower with the output connected to the (-) inverting input and the oscillator (or speech or music) connected to the (+)...
  9. audioguru2

    TRANSISTOR ATTENUATOR?

    Hi Alun, Never mind the DC current, the thing is cap-coupled. The junction of the input resistor and the feedback resistor is a low impedance point at AC because as the input swings positive, the output swings negative and vice-versa. Therefore the junction is a virtural-ground like the...
  10. audioguru2

    n-chanel enhancement mode power mosfet

    Hi Goatman, You're welcome. ;D Haven't you burned-off the tread on the tires yet? ;D ;D
  11. audioguru2

    Screen Resolution

    Hi Miles, Don't try to see what happens when you make fun of a Mod. He, he. ;D I'm glad you found the source of your fuzziness!
  12. audioguru2

    Screen Resolution

    Hi Miles, Only your schematics are fuzzy when opened or downloaded and seen on my viewer. I tried reducing my screen res from 1152 X 864 down to 1024 X 768 and everything was bigger on the screen but still only your schematics looked fuzzy. My previous post got deleted somehow, but did you...
  13. audioguru2

    n-chanel enhancement mode power mosfet

    I don't think the relay contacts will care about inductive spikes from the motor. Whatever drives the relay coil could easily be destroyed by the hundreds of volts produced by the high inductance of the relay's coil when it is switched off. Hold the bare wires connecting a relay's coil to a 9V...
  14. audioguru2

    TRANSISTOR ATTENUATOR?

    Hi Alun, You mean the negative feedback decreases the input impedance, don't you? The input of the transistor is approaching being a virtural ground. I think that the input impedance is very close to the value of the 47k input resistor. Is your sim program any good? Frequently they screw-up on...
  15. audioguru2

    designing of third harmonic filter

    Hi Sarwar, Welcome to our forum. ;D The design of a filter depends entirely on its frequency that you didn't mention. 150Hz? 3kHz? 30Mhz? 3Ghz? Instead of a filter it might be easier to make the source more linear so it doesn't clip or produce 3rd harmonic distortion. What is it? If the source...
  16. audioguru2

    741 Offset voltage problem

    Hi Sherbo, You are overlooking the 741's common-mode input voltage limit of 3V max from the positive supply or from ground in your single-supply circuit. An LM324, LM358, MC3458, MC3307x or MC3317x can operate with their inputs at ground but not near the positive supply. A TL07x can operate...
  17. audioguru2

    TRANSISTOR ATTENUATOR?

    I think the gain/loss is a lot more complicated: 1) Much of the input current through the 47k resistor is dumped in Rbias. 2) The input impedance of a transistor without an emitter resistance is fairly low so also attenuates the current through the 47k input resistor. 3) In addition to current...
  18. audioguru2

    Hey! Hey!

    Hi Tekker, Welcome. ;D Didn't I talk to you on another site? I like your avatar. ;D
  19. audioguru2

    n-chanel enhancement mode power mosfet

    He, he. I'm wrong! Leave them running for a while. Notice how they lose their sync? ;D [move]1
  20. audioguru2

    n-chanel enhancement mode power mosfet

    BTW, somewhere you posted a coloured statement that didn't move. I think the moving command should be the final one. This image is "marquee'd" then coloured: Move!                Move!                Move!                Move!                This image is marquee'd last: Move!             ...
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