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  1. audioguru2

    rf power amp

    Your power supply voltage determines how much power the RF amplifier makes since it has such a high input level. Didn't you see this thread about FM transmitters with RF amps? http://www.electronics-lab.com/forum/index.php?topic=6263.msg40062;topicseen#msg40062
  2. audioguru2

    rf power amp

    You forgot to say what RF frequency.
  3. audioguru2

    any pinoy here pm me

    A 555 oscillator that is driving a capacitive-coupled rectifier will give much more negative output current than an ICL7660, but has a two-diodes voltage drop. A car stereo power amp that has an oscillator driving it and it is driving a capacitive-coupled rectifier will give much more negative...
  4. audioguru2

    Question about amplifier

    You can look at spec's for audio power amp ICs. A little LM386 gives 300mW to an 8 ohm speaker and has a quiescent current of 4mA. A car radio power amp gives 4W to a 4 ohm speaker and has a quiescent current of about 30mA. A higher power home stereo amp gives about 70W to an 8 ohm speaker and...
  5. audioguru2

    500W 12v to 220v Inverter

  6. audioguru2

    amplify the power (infrared)

    Correct. Then the voltages for Q2 must also be wrong. I notice now that the voltage divider of R4 and R5 has its values too high for 1.9V on the base of Q2, when Q2 has 31mA of current in the LEDs. R4 should be 5.6k and R5 should be 1.5k. The resistor that I added in series with the base of Q2...
  7. audioguru2

    rf oscilaotrs

    Your other post has replies with circuits that detect the RF oscillator in your cell phone (mobile phone) when it transmits a signal that it is on and is operational just before it rings an incoming call. You don't need to make two posts about the same topic. You don't need to make an RF...
  8. audioguru2

    4 Watt Fm

    You won't find a trimmer capacitor that goes down to zero pF. There are many of them that go from a few pF to 30pF or 35pF. If the tuning needs to go to a higher frequency then subtract a turn or two to the coil. If the tuning needs to go to a lower frequency then add a turn or two to the coil...
  9. audioguru2

    amplify the power (infrared)

    Did you try it with the AM envelope detector circuit I sketched? I think you need to use an oscilloscope to see if the transmitter and receiver parts are adjusted properly for full modulation.
  10. audioguru2

    Make a Microwave oven on a small-scale

    Hi Dazza, It is good that you are back. ;D
  11. audioguru2

    amplify the power (infrared)

    No Ryan. A resistor and capacitor is not an AM envelope detector. Also, a 40 ohm resistor and a 0.1uF capacitor is like a dead short at 38kHz to the output of an opamp. The minimum load for most opamps is 2k ohms. An AM envelope detector is a diode followed by a filter capacitor. Look at the...
  12. audioguru2

    amplify the power (infrared)

    Yes, the capacitive reactance of a 0,1uF capacitor is about 40 ohms at 38kHz, but which resistor and which capacitor?
  13. audioguru2

    amplify the power (infrared)

    The two resistors that I boxed with red in my receiver circuit reduces the gain. They should be adjusted so that the circuit doesn't overload with too much signal. Did you make an AM detector (envelope detector) to demodulate your AM modulation? What range are you trying?
  14. audioguru2

    Op-amp or trans-impedance amplifier

  15. audioguru2

    NiMH Battery Pack Charger

    All battery manufacturers have info on their websites. My favorite is www.energizer.com . At the top of the 1st page select Technical Info, then select Ni-MH Rechargable. You will see a link to their excellent tutorial and a datasheet to their AA cells.
  16. audioguru2

    amplify the power (infrared)

    Sorry, I forgot to attach my sketch. The resistors are boxed in red. Yes. Your receiver circuit needs one.
  17. audioguru2

    amplify the power (infrared)

    Your IR receiver probably has a strong output at 38kHz now but you can't hear a frequency so high. Therefore the receiver needs to feed an AM detector diode and filter to recover the modulation. The transmitter circuit has two very important resistors that need adjustment. See my sketch. You...
  18. audioguru2

    High Voltage Cap charger

    Make the oscillator run at a frequency high enough that the capacitor's charge pulses occur very frequently. Use a high value capacitor so it won't discharge much into its load. Use a more powerful (higher current rating) transformer that has less resistance so it can charge the capacitor quicker.
  19. audioguru2

    High Voltage Cap charger

    The little 9V battery might run down before the capacitor is charged enough. You are absolutely correct and I was wrong! ;D :-[ The peak voltage of a sine wave is 1.414 times higher. This project has a square-wave so its output voltage will be 690AC and 690VDC. Actually, the DC voltage will...
  20. audioguru2

    High Voltage Cap charger

    Hi F4, An IC555 timer's output is rated at 200mA of current, and a little 9V battery can supply that much for a while. So you could make the IC555 oscillate and connect its output to the low voltage wires of a 230VAC to 3V/200mA power transformer. The resulting 690VAC could be rectified and used...
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