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  1. K

    URGENT HELP PLEASE

    I think they call this keying. All you need is to adjust the carrier with the message. Transmit a series of pulses. This way you don't have to modulate the carrier. Modulation is done when the information has a lot of changes to it and the change is such that you can have any number of values.
  2. K

    DC Motor Speed Modulation

    It seems to me you could use any waveform to drive a motor efficiently. You don't have to PWM. In PWM you change the voltage to zero which is sort of like a signal. All you have to do is change the voltage. You don't need to run at full speed and then drop it to zero. You can use any voltage...
  3. K

    AC/DC adaptors: voltage over normal?

    You should get the correct voltage if the current is what is listed on the device. I think the DC adaptors are unregulated to boot. The device you plug it into will have a regulator. Regulators are designed for maximum benefit when the current is just right. That is why you should not double up...
  4. K

    Digital multimeter powered by adaptor?

    I took my radioshack multimeter which came with two small batteries and replaced them with two D cells. It works fine. Unfortunately it works. Thoeretically if it were designed to perfection it would not work. But this is just another cheapo design.
  5. K

    pulse detecotr type circuit

    Here is the circuit. You don't need rectifier diodes. It will give you the positve cycle on demand and the negative cycle going positive on demand.
  6. K

    The simplest audio amplifier

    I hope this circuit is better. Sorry.
  7. K

    The simplest audio amplifier

    deleted
  8. K

    Transistor as a switch

    A transistor switches between two voltages. Since it is a current controlled device it can't actually act like a switch. You have to set the current with the voltage at the emitter base junction. However many circuits do utilize the cutoff and saturation feature. I have operated a transistor in...
  9. K

    The simplest audio amplifier

    A guy in the chat room wanted to auto stereo amplifier. I suggested he use a 3A transistor but needs the negative supply. I noticed the 555 timer can be configured to give the -12 volts output. But of course the current is too low. Could somebody post the simple solution.
  10. K

    SAW filters

    I have heard that SAW filters have good attenuation. Has anybody ever used them? I would think their charactersitic is very useful. Could somebody post a circuit with them. I am just curious. I see now that they have funny response to them. Maybe this is the reason for their lack popularity.
  11. K

    Need VALUE for resistor..

    There is a better way to accomplish this task. Take the output of the rectifier and add a series capacitor at 1000uF, a series resistor at 20 ohms, and a capacitor to ground at 1000uF. Tap the output across the capacitor to ground. This should give you the DC your require and extra filtering...
  12. K

    Why 50 50 50 maximum power

    The term nonresonant applies to the condition where the reactance is cancelled out and the line impedance is equal to the source impedance is equal to the load impedance and describes maximum power transfer. The maximum power transfer is difficult to see because you might think that a high...
  13. K

    Dont understand Schematic

    I think I recognize this circuit. Is this a pushbutton activated oscillator output? Like a telephone transmitter.
  14. K

    Newbie question on terminology

    A latch is most useful. It is a storage device. Once it is set or reset it will hold the result. Normally a high on the input is used to set or reset and a high on both will, as matter of fact, reset the output.
  15. K

    Energy bands

    Doesn't it seem odd that the current in p type is within the covalent band while the n type current is in the conduction band. I would suspect a property difference in there somewhere. Copper has overlapping energy bands whereas it takes the same amount of energy to push an electron in the...
  16. K

    Barrier potential discrepancy

    Just as a side note there is current before .7v is reached. The current is created by the movement of electrons as they are reducing the depletion region. I say reducing the depeletion region because when there is no voltage applied to the junction, the depletion region is wide. When you reverse...
  17. K

    Question from a student about amps

    It is the only two functions that you can compare. The question is why not take the difference instead of division. Division can make two numbers identical while a difference can't. 100-5=95,200-10=190. These two equations have the same result of 20, by division, but the difference is 95 and...
  18. K

    Interpreting Datasheets

    That is an interesting subject. It can be desireable to bias a component outside the datasheet. My gripe is with the opamp parameters at high frequencies. Why operate at such a high frequency just because you can. I think it's too nonlinear. It's not great that you want to attenuate the spectrum...
  19. K

    Newbie question on terminology

    The high impedance means the voltage applied does not produce a current.
  20. K

    non logic level multiplexar

    What if I want a multiplexar that feeds through the input voltage. This way I could monitor a bunch of voltages by selecting one line and this goes to an A/D. In other words I want to use one A/D and monitor the voltages of many inputs. Does there exist a voltage follwer multiplexar?
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