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  1. BobK

    LM7805 - Linear Voltage Regulator And DC-DC Converter Analysis

    The 7805 is a linear voltage regulator. It samples the output voltage, compares it to a reference voltage and then adjusts a pass transistor to keep the output voltage at 5V. Bob
  2. BobK

    Transistor help!

    The base emitter junction is a diode. The base current flows in the same way as current flows in a diode. Bob
  3. BobK

    High Current 12volts DC Power Supply

    That's a lot of power for the dollar! Bob
  4. BobK

    LM741 Integrator and Audio Amplifier circuits

    rail to rail outputs Bob
  5. BobK

    LM741 Integrator and Audio Amplifier circuits

    In an integrator, the op amp is used to charge a capacitor with a current that depends on the input voltage. The voltage on the capacitor then follows the integral of the input voltage over time. Bob
  6. BobK

    Dodgy Power Amp Design

    I really can't see how it can work with the virtual ground. All of current in the output circuit has to come either from the opamp, which can supply only about 20mA or from the capacitors, which can supply the current, but the ground voltage would go up and down with it. Have you tried...
  7. BobK

    9V Power Supply using Solar Panel

    You can get 18650 cells and an AC powered charger for < $10 on ebay. Have you given up on the solar panel then? Bob
  8. BobK

    motor

    A stepper motor will require a driver board. You cannot just hook it up to power and make it run. Bob
  9. BobK

    9V Power Supply using Solar Panel

    Lithium is a good choice. You would want about a 2000mAH one to gaurantee 1 hour at 1 Amp on a charge. That would be using 11 Watt Hours. To charge them from a 2.5W source would take about 6 hours of peak sunlight, or realistically, more like 12 hours since it will not produce peak power...
  10. BobK

    5V Pulse Amplification

    If you read a little more, you will find the the LM324 cannot output a voltage all the way up to the supply. That is why I said use 24V. That might not even be enough, depending on how much current you draw from it. Bob
  11. BobK

    Dodgy Power Amp Design

    Connect though a sufficiently large capacitor to 0V. Bob
  12. BobK

    9V Power Supply using Solar Panel

    The best rechargeables are Li Ion. These have a voltage of 3.7V / cell. so a 3 cell battery would put you in the 9-12V range (11.1V). Second best would be NiMH which are 1.2V, so 7 of them to get 9.4V. If you have higher current requirements, a 12V sealed gel lead acid battery might be best...
  13. BobK

    Dodgy Power Amp Design

    How is out connected? If it is returning to the virtual ground, that is not going to work, it cannot supply enough current and the virtual ground will be varying all over the place. Bob
  14. BobK

    9V Power Supply using Solar Panel

    Your math is now right, but there are other problems. What kind of batteries are you talking about? I do not know of any batteries that are rechargeable and 1.5V per cell. NiCad and NiMH are 1.2V per cell. So 6 batteries will get you 7.2V, not 9. Then there is the problem that you cannot...
  15. BobK

    The Solar Powered Glove: Need Advice!

    Easy! Just wear black gloves. They will capture nearly all of the energy falling on them from the sun and convert it into heat. Bob
  16. BobK

    Simple power supply questions

    Insufficient battery power. Bob
  17. BobK

    Design a FET-Based Amplifier

    I thought so. So this thread should be moved to "homework help". Bob
  18. BobK

    Design a FET-Based Amplifier

    Buy an opamp for about a quarter. Bob
  19. BobK

    Another LED-diodes topic

    27 is a standard resistor value. Bob
  20. BobK

    5V Pulse Amplification

    Use 24V for the op amp supply. Bob
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