Search results

Search Forums New Posts
  1. K

    Power Amp

    There are a few things worth noting about power amplifers. They use high current transistors and here are some characteristics. As it turns out, the high current leads to large voltage drops across the resistors unless you use low value resistors. Power amps drive loads that require high...
  2. K

    COILED RESDISTOR?

    One time at this place I worked, they had these waveguide filters that needed to be tuned. The part that you tuned appeared to be a capacitance screw that had a metal outside and a core on the inside. You put the screw into the waveguide and from there you could adjust the protruding capacitance...
  3. K

    Beta of the BJT

    Just a little something I found out about beta. At low currents the beta is low. As you increase the collector current the beta get's higher. Increase it more and the beta goes lower. So there is place on the current curve where the beta is at a high point. I don't know what this means but I...
  4. K

    How small will they go?

    Interested in memory? Do a search engine on vitual memory and memory interleaving. I'm not a programmer but I picked these terms up in a book and found them quite interesting.
  5. K

    Digital mishaps

    I am curious when it comes to digital communication errors. We know that that there are error detection schemes in use to help catch these errors. We also know that these errors occur in products that have been fully tested and have no hardware problems. One question I have is why are these...
  6. K

    Laser&Electro-Optics

    Hi. I have worked on CO2 LASER's before. They were 20W to 50W at about 20K nanometers. There was this thing called breakdown in which the combined sine waves collapsed upon application to the tube. They tended not to and you had to adjust this variable capacitor to get it to. There was this...
  7. K

    TRANSISTOR ATTENUATOR?

    Hi guys. I just wanted to share the problems I was having with theoretical design. I have something interesting that you might like. Suppose the signal was applied to the base of the PNP. And suppose a much smaller signal were applied to the base of the NPN. What I am getting at is that...
  8. K

    TRANSISTOR ATTENUATOR?

    I just wanted to clarify another point. We are so accustomed to using this principle that we forget what the situation is about. Whenver your dealing with a signal and a DC supply voltage, it's easy to say that the change in voltage over the impedance is the change in current. That is with a DC...
  9. K

    TRANSISTOR ATTENUATOR?

    Hi Audioguru, I'm glad you were able to identify the type of cirucit I was describing along with the low impedance observation. I think I used a resistor to increase the impedance. Other than that, here is an acceptable gain circuit. The nice thing about the common base is that the emitter...
  10. K

    TRANSISTOR ATTENUATOR?

    I have seen where a signal can originate at the emitter of a transistor, or at the base. Assuming a base resistor, it seemed possible that the signal applied to the emitter would be larger at the base because of the base current and the resistor. And in fact there is a signal at the base, but it...
  11. K

    BASIC FEEDBACK THEORY QUESTION

    Everything you say seems right to me. But can't we explore it a little further. I have read all that stuff and it gets very repetative. It seems like that old list of ideal opamp parameters is always popping up. The circuit isn't that bad. I know that the output resistor isn't a collector...
  12. K

    BASIC FEEDBACK THEORY QUESTION

    Yes, I know. Maybe I would go with an Rf of about 10K. Of course the opamp input current is well below the feedback current. Remember that article about using a 10K output resistor to the negative supply. That worked great to get a difference. I think that this should work fairly well too. But...
  13. K

    transformer windings

    I think it is just a theory problem. You see, I like to follow the polarity of a circuit, especially with transformers. In this case, both supplies share the same ground, but they are different windings. You can only follow the polarity when analyzing each winding separately. Apparently it does...
  14. K

    BASIC FEEDBACK THEORY QUESTION

    The ideal parameters of an opamp are building blocks. I have seen zero difference between the inputs at low gain, but not at higher gain. Imagine an amplifier meant to amplify so much that you use it for very low gain. Maybe even a gain of only one, a buffer you know. Anyways, I like to see and...
  15. K

    transistors

    Beta is determined by the current capability of the transistor. A high current transistor has a lower beta. If you want to know the truth, I like low beta because a beta like 50 is more likely to remain near 50 while a high beta of 500 will not hesitate to go to 450 or 550. Am I following any...
  16. K

    opamp won't output zero

    Audioguru, I don't want to post my circuit when it's easy to explain. All I am trying to do is experiment. Searching for a broader meaning. I know you don't think the only way to lower gain is with negative feedback. I mean, if I wanted, could I not design an amplifier with whatever gain I...
  17. K

    opamp won't output zero

    Audioguru, I like to think in terms of collector and emitter resistors. A base resistor is like an emitter resistor and an output resistor is like a collector resistor. This is how I lower gain. I make sure the output resistor is at least 10K and that I don't overload my generator. It's not...
  18. K

    120 VAC

    Yeah, but even though the AC impedance of the capacitor is low, you still get all the voltage because there is not a divider. All the transformers output will end up across the capacitor. Well, I should say there is a small divider when you have a diode in there, but the diode can't drop a lot...
  19. K

    opamp won't output zero

    I did this experiment with an opamp and found that the output had quite a bit of DC offset. It looked as though the difference between the inputs was being gained too much. And yet I was able to get a reasonable sized amplification. So if it's gain, which I think it isn't, why is it still high...
  20. K

    120 VAC

    The AC delivered to your house is apparently very sinusoidal. This is a claim I have read. So why a sine wave. Why not a triangle. It is because the sine wave has a low rate of change as it approaches the peak of the cycle. Sometimes the AC is low enough frequency dependent on your circuit, this...
Top