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  1. K

    transistors

    Hi Audioguru. I think that feedback, zero time difference, is only there as a necessity. It let's current flow around the opamp. But of course why do you need that. It just so happens that when you put a resistor from the output to the  inverting input, your gain looks like it mimicks the...
  2. K

    RC time constant

    Here's the link. It's a bit long, but look where it talks about the time of the signal and the RC time constant. http://www.kpsec.freeuk.com/capacit.htm I you want to pass a sine wave through a capacitor, you have to know how a capacitor charges. There is a graph of voltage and time. So, you...
  3. K

    transistors

    I think that high beta transistors are considered high gain because of the current multiplication. Generally, to get gain, you look to the collector and emitter resistors. It is always safer to play the voltage game. What you end up doing in the current gain scenario is to lower the change in...
  4. K

    Fet driving question

    As far as I have read, there is an input impedance to the FET. It seems obvious that one may want to divide down the signal. Something to be said about resistors. Not only do they reduce the signal, but they also reduce the noise. If for any reason your threshold of noise is too high, just...
  5. K

    3dB point or pole

    What I normally use is db = 20logVout/Vin. Since you are dealing with a capacitor, you might as well use peak to peak voltage. You will notice that you could use the instantaneous voltage, the results are the same, but you should not because there are many instances where the instaneous voltage...
  6. K

    BASIC FEEDBACK THEORY QUESTION

    I think the real purpose of having differential inputs into an amplifier is so that you can apply two signals on a pn junction and have the resulting voltage be gained. This is what you do if you want to combine two signals but in a way that is different from using resistors. You could use...
  7. K

    Automotive 12V to +-20V converter

    Can you see the polarity problem I am talking about? Just scribble it down on paper. The polarity of the coil for the positive supply is opposite for the negative supply. I am very skeptical about this situation. If it does not work on paper, there is something screwy going on.
  8. K

    Automotive 12V to +-20V converter

    Audioguru, read my last reply. It will explain it. It's the polarity of the coil. Trust me. If your looking for the positive supply, the polarity of the coil remains the same for both cycles. But if your looking for the negative supply, the polarity of the coil remains the same for both cycles...
  9. K

    Automotive 12V to +-20V converter

    Stick with me. I'm on to something. It is not a bridge rectifier. I was wrong. But the coil is playing a weird part in this. Follow the polarity. I am right. Follow both the negative cycle and the positive cycle. Try using one half of this circuit. Try the positve supply voltage. Notice that...
  10. K

    Automotive 12V to +-20V converter

    I have a general question about the circuit. It appears the transformer combo will not work. I have searched for a mistake but I still cannot make it work. I think what is missing is that a rectifier bridge will not give you the desired results. You have to have a center tapped transformer to...
  11. K

    more help on h-bridge

    One thing about the 555. This is a very simple circuit that does strange things. It is best, if you are going to use one, to figure out what the circuit will do if you are able. I have spent hours upon hours with even the simplest of circuits to figure out how they work. So be wary, you may find...
  12. K

    Fet driving question

    Okay, what is going on with the FET? Isn't there even the smallest amount of gate current. Doesn't it have an input impedance and isn't it gm dependent. Rin is equal what? Maybe I'll get it straight. Okay, the input at the source of a FET is 1/gm. I think that is right.
  13. K

    HELP! project abt DC power supply.

    In another post long ago, I had this idea. A voltage multiplier, which is typically low current, makes a good DC source from an AC or analogue signal. Of course in order to make them high current, you need high capacitance. High capacitance makes them low voltage capacitors. Therefore, it is...
  14. K

    frequency detection without oscilloscope

    An IR transceiver is meant to communicate by means of high and low pulses. I think it is for two reasons. One may be that the data is already digitized. Another may be that, depending on your requirements, the transducing effects don't give you a pristine signal. Could somebody explain here how...
  15. K

    transistor voltage regulator

    Something worth noting about regulators. I have this idea that major power supply manufacturers subscribe to this idea. If for every current you can maintain the same voltage, you are a winner. I have often wondered how you can purchase a supply and be guaranteed of the voltage at virtually any...
  16. K

    theory question!!!???

    It is interesting that when I think of two and three phases I think of that silly sinusoidal picture of sine waves superimposed. How are you supposed to know what the voltage is actually doing. Does it add? Does it subtract? A total conspiracy. Here's something that comes to mind. Whenever you...
  17. K

    Final Year Project For Electronic Egn

    Electronics is not an easy study. You might get a little frustrated when you try to build and test a circuit. What you will find in many instances is that a designer will utilize block diagrams, put together a multichip monster of a circuit, and realize success or failure by the presence or...
  18. K

    C_B transistor impedance matching

    Not much is ever said about impedance matching. Impedance matching implies that you are trying to get two impedances to be equal. And they do this for a reason. I think it is because in some circumstances you want a certain impedance, whether it exactly matches or not may not matter. Just as...
  19. K

    Light bulb dimmer

    Hi
  20. K

    Light bulb dimmer

    What is the construction of a light bulb dimmer?
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