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  1. K

    70 volt regulator

    The regulator is a motorola 513 je 800. I think the je800 is the part. The zener is on the emitter of the NPN control transistor. The collector goes to the control of the regulator. The base is connected to the ouput through resistors. The zener gets its voltage this way. I wonder about the...
  2. K

    RJ45 network card to IR

    I don't think the voltages are respective. You have to connect the 9v with the 5v somehow. What about the signal at the 9v negative terminal. If you have a signal there, you will have a signal on the other side. You have the 5v connected to the 9v through the photodetector and the 5v connected...
  3. K

    OPAMP questions

    Opamp compensation serves another purpose. The input capacitor, often seen with compensation, changes the critical frequency. If you notice the bode plot graph, you will see that the critical frequency can be anywhere. When you add a capacitor, the critical frequency moves from the 40db per...
  4. K

    Power Supply +5v with Zener

    The circuit I was refering to is a commercial circuit. A resistor could replace the zener, but why did they use a zener. This is a simple transistor biasing arrangement with the zener at the emitter. By the way, the difference in a regulator and a zener is not much. The reverse bias zener is...
  5. K

    OPAMP questions

    I don't think opamps would be very popular if the phase shift were a problem. The problem is that the opamp could become unstable.What does this mean? The input signal can not drive the output to it's voltage level. Am I right? This would be because of the negative feedback of the individual...
  6. K

    transistors

    Is it common practice to use higher voltages with transistors if the current is low? I have read that the current should be half the rated current. I suppose if you want to use a higher voltage, then low current is alright, but not optimum.
  7. K

    Impedance matching

    I want to use a 50ohm cable. This gives you capacitance as well a inductance. Somehow the load impedance will affect the line impedance. If you say the load impedance is closer to a short, then the length of the cable should be chosen to be a series inductor capacitor at the resonant frequency...
  8. K

    regulators

    I believe the output capacitor is tagged on to some power supplies mistakenly. If you were to take the most simple circuit and want a supply that will maintain a voltage, then I doubt it would include a large capacitor. A constant voltage with a change in current is merely a simple task. Most of...
  9. K

    Power Supply +5v with Zener

    I have seen a power supply with the zener controlling the emitter voltage of a darlngton. The collector goes to the control. The input is also fed to the control through a resistor network. Why can't a resistor be used in place of the zener in this situation? I am thinking the signal works...
  10. K

    70 volt regulator

    I can't find the data sheet on the regulator. I know the circuit was operating at 25vdc with the input, the ouput, and the control all at this voltage. It might be a variable voltage regulator. I must have the data sheet to do anything with it.
  11. K

    ttl or gate

    The problem with a simple gate is the slew rate. The gain is not high enough through the transition. A low to high transition will not produce a high quick enough. If you make the gain very low with a pulse input, you get a pulse output the with the same reduction that you would have with a sine...
  12. K

    RJ45 network card to IR

    I am perplexed. Why is the photodetector forward biased? The gate must me CMOS. Am I right? I have another question. The original circuit is what I am concerned with. It has a battery that works in conjunction with the power supply, but without a common ground. The use of devices without a...
  13. K

    Impedance matching

    I want an easy way to determine the matching characteristics of a line. I want the output device to be any resistance, the input device to be any resistance, and the cable a 50 ohm. What is the length? How can we determine this without going to any trouble?
  14. K

    70 volt regulator

    I found the zener to be a 8.5v approx 1.5 A . This would make the control voltage approx. 12v because of the transistor. The input voltage is approx. 70v though. This is very high, but there are large divider resistors which means there is not much current from input to the control. The current...
  15. K

    70 volt regulator

    What you are saying is that a large capacitor on the output will allow more current when there is a sudden current burst.
  16. K

    70 volt regulator

    I already took apart the circuit. The large capacitor on the output is open for debate. I have seen smaller capacitors on the output. I think this is correct because the voltage regulator regulates not only the dc, but the fluctuation as well. If you design the voltage regulator to have a small...
  17. K

    70 volt regulator

    I have this power supply that I was given that takes the 120vac and converts it to 50vac. The current of the bridge is 1.5A max. The regulator has a control line, input, and output. The output is fed to the base of a darlington and the collector goes to the control. The emitter has a zener diode...
  18. K

    RJ45 network card to IR

    I don't think the outputs are differential like they are supposed to be. The outputs are complementary. The purpose of the differential is to treat the inputs as two signals. Sometimes this is better than using ground because the ground can contain many signals.
  19. K

    regulators

    I am perplexed at the use of large capacitors on the output of the regulator. I have seen small ones used in their place and I think this is correct. The regulator would have trouble trying to change the voltage with a large capacitor. And remember that the DC voltage is always determined by the...
  20. K

    ISA Bus oscilloscope Project

    I would guess that the timing is the most important aspect. What is the C function for a delay? You will probably need quite an interface for the computer. The rate of the A/D would not coincide with the computer. Can anybody suggest an interface device. Would this be the job of a PIC? Doesn't a...
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