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  1. K

    Re: Help with LM386 Amp

    C7 also prevents DC loading of the amplfier and doesn't affect the impedance. It might be added to help prevent high frequency oscillation, and it may allow for a more constant impedance between the high and low frequencies.
  2. K

    running 12v ac device on 12v dc

    Power inverters, which are sold in stores, are more reliable and won't damage the mixer. You might want to have the circuit designed and funtioning before testing it out on the mixer.
  3. K

    Re: Band Pass Filtering & Impedance Match

    An LC filter uses larger value components than what is concerned with impedance matching. It would be the main filtering section and the impedance matching done to help eliminate problems caused by a transmission line or requirements of the devices connected to it.
  4. K

    Re: Ldi/dt of an inductor

    An inductor can produce a different result depending on the waveform you apply to it. Sometimes waveforms are not constant and may have periods of DC, AC, or pulsating DC. A diode in parallel with an inductor is sometimes used.
  5. K

    Battery Charging - Help?

    It might depend on the the size of the battery. I'm not familiar with a microcontroller based battery charger, but it sounds complicated. I think the concept is very good. But even battery chargers you buy from a store I doubt use microcontrollers. Probably because the cost/benefit does't isn't...
  6. K

    Determining the frequency of a transient

    The rise time is proportional to the time of the square wave and is made by amplifying the sinewave using high gain. So it's dependent on gain and the time of the sine wave. However, the time of the square wave is the biggest factor when comparing the rise time of let's say a 1KHz square wave to...
  7. K

    Are datasheets important?

    According to your post, you added internal resistance to the 1Kohm for 1900ohm. But you said if it's less than 10K you subtract internal resistance. It's not subtracted.
  8. K

    Are datasheets important?

    Interesting point, if less than 10Kohm subtract the internal resistance. The impedance does look too low for MOS. But nothing I design lasts more than 3 hours, so it looks like a plausable design to me.
  9. K

    Are datasheets important?

    Maybe the resistor value in the RC common network is a factor. If someone uses 47Kohm and 100nF for the RC, then uses a 1Kohm resistor in the RC common network, then the time constant will be affected. So a small resistor like 10 Ohms might be more accurate if you used a 47Kohm and 100nF.
  10. K

    Ft of the transistor

    A strong base signal could be developed at the base, bringing the base in phase with the emitter, which is the case of a common emitter or common collector.
  11. K

    12 V DC to a 220V AC Inverter AMplfier Design

    Hi AN920. I looked at your square wave inverter again. It looks like at 50% duty cycle oscillator, both outputs produce 25% duty cycle. Reducing the duty cycle of the oscillator means that both outputs have even lower duty cycle, and the two waveforms are offset from each other. Now I am just...
  12. K

    Ft of the transistor

    I see. The emitter resistor has little affect on the amount of feedback or phase shift. C5 divides by beta making the feedback almost totally capacitive. That means the collector signal is in phase with the emitter signal. Too strong a base signal would put the base signal in phase with the...
  13. K

    Frequency response for a transistor amp.

    I think the simulation is wrong. I don't see where you would get a change in response at Xc = 13000.
  14. K

    12 V DC to a 220V AC Inverter AMplfier Design

    Hello AN920. Your square wave inverter circuit produces a clock and a clock not? Why does it have so many gates and how does the flip flop help. A flip flop has an extra gate of time delay, which would conflict with that parallel gate.
  15. K

    SIM cards

    I bet you can use phone SIM cards in other applications. I have seen all sorts of high technology products used in custom test jigs.
  16. K

    Frequency response for a transistor amp.

    Walid, I think the response is flat where the reactance equals the resistance. The lowest value always carries the most weight. But when they approach each other in value, the impedance is severely affected by both.
  17. K

    Ft of the transistor

    The signal at the emitter of the oscillator leads the collector signal by 90 degrees because of C7. That means the emitter lags the base by 90 degrees. I also understand that simple oscillators are just that, simple. They are not signal amplifiers.
  18. K

    Ft of the transistor

    Class C used for power audio creates an abridged version of the audio signal. And that means you lose a lot of what was in the audio signal. The oscillator looks like it has 90 degrees feedback. Have you tested this transmitter with a simple receiver? How does it sound?
  19. K

    Ft of the transistor

    I was talking about the oscillator itself. If we were to take away the modulation, the oscillator would be of a certain quality. Your saying the LC produces a good oscillator regard less of the transistor operation. The change in collector current looks excessive. But your saying it has no...
  20. K

    Ft of the transistor

    A PLL has to control the output of a VCO to make a good sinewave. If you don't control a parallel LC circuit, how can it make a good sinewave regardless of how the transistor is operated? I would think a transistor operated most linearly would make a better sinewave.
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