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  1. AnalogKid

    Astable Multivibrator Circuit (Flashing LEDs)

    Duke is correct. Each transistor is turned off by a negative spike approximately equal to Vcc. If the peak value of the spike is greater than the transistor reverse Vbe rating, repeated applications of the spike will weaken the transistor even if the spike current is limited. One solution is...
  2. AnalogKid

    Astable Multivibrator Circuit (Flashing LEDs)

    https://en.wikipedia.org/wiki/Multivibrator ak
  3. AnalogKid

    Question about transistor

    Because all language is subjective, all definitions rely on other definitions. Calling something a definition is not a license to misuse or misapply those that came before. ak
  4. AnalogKid

    Question about transistor

    is wrong. ak
  5. AnalogKid

    Connecting a vintage microphone to a PC

    For speech recognition, high frequency perception is overrated. POTS (Plain Old Telephone System) has a brick-wall bandpass of 3.3 kHz to 4 kHz (it varies among individual systems). And yet, people can interpret not only speech, but the emotion in a voice. And remember, the phone was invented...
  6. AnalogKid

    Want to make an Electromyography amplifier circuit.

    The #9 schematic is worse than the #4 schematic. There now is a DC gain of 9,966. This means that a signal of only 1 mV at the output of U2 will saturate the output of U5. Also, as mentioned above, all of the gain setting resistor values should be increased by 10x. In this way the opamp...
  7. AnalogKid

    Want to make an Electromyography amplifier circuit.

    U3 and U4 combine for a DC gain of 55. Any DC offset error out of U2 will be amplified by this amount, which may be enough to cause a problem. Consider AC coupling between U3 and U4 to reduce this. You are using the input diff amp as a single-ended opamp. That's ok, I guess, but you are not...
  8. AnalogKid

    Connecting a vintage microphone to a PC

    Based on the datasheet, yes. If page 4 really is the internal schematic, then this mic has a compressor or AGC (automatic gain control) circuit to even out changes in loudness caused by turning you head away of becking away from the mic. ak
  9. AnalogKid

    Hour meter for laser cutter

    22K and 0.33uF looks like 7 milliseconds to me, less when you figure in D1's Vf. ak
  10. AnalogKid

    Hour meter for laser cutter

    Assuming the LED Vf = 2 V, the LED current is only 0.6 mA. Seems a bit low, but I don't know the LED part numbers or the viewing environment. Also, while the 40106 high and low output currents are spec'd the same, in my experience the 40106 can sink more output current than it can source (for...
  11. AnalogKid

    555 timer one shot question

    How short of an output pulse do you need, max and min values? Mechanical switch contacts "bounce". Then the switch goes click, the contacts come together, bounce off of each other, and come together again, many times. There can be dozens of on-off cycles in a few milliseconds. So there is a...
  12. AnalogKid

    Popping sound when switching microphone with relay

    I have used you alternate connection in automotive applications after seeing that TI built that technique into some of their power driver ICs. It works well, and keeps any residual inductive kick effects off of the power rail; not a big problems in cars, but it could matter in an...
  13. AnalogKid

    Popping sound when switching microphone with relay

    ??? Depends on the zener voltage. A 1N4001 is a rectifier rated for 50 V PIV (peak inverse voltage). But it does break down eventually if you raise the reverse voltage high enough. In effect, it is a 100 V zener with horrible accuracy, about +/-25%. For a 24 V relay coil, a 30 V or 33 V...
  14. AnalogKid

    Popping sound when switching microphone with relay

    Correct. 20 A, maybe. 10,000 times less, no. ak
  15. AnalogKid

    Popping sound when switching microphone with relay

    The nominal coil current is less than 9 mA. Go with the 1N914 / 1N4148. It has a lower conduction voltage and much faster switching speed than the 1N400x series. Both of those things should increase its effectiveness. ak
  16. AnalogKid

    Few questions (multiple-choice)

    Transformer question - correct. Voltage regulator question - I agree, none of the choices are great. It might be a mis-translation (to go with the misspelling). There is no active filter question. For the active oscillator question - incorrect. Surface mount ceramic capacitors have...
  17. AnalogKid

    Few questions (multiple-choice)

    Tell us your answers and we'll tell you if they are correct. Don't just guess; explain your thinking. ak
  18. AnalogKid

    60 Hz line frequecy divided to 1 pps

    This is not the case. Your "service provider" has nothing to do with line frequency. That is set at the power generating stations, which could be 1000 miles away. Also, AC power is created and delivered over a multiply-redundant grid of interconnections, so at any moment your power could come...
  19. AnalogKid

    60 Hz line frequecy divided to 1 pps

    Even better than the US link above. * * * * ak
  20. AnalogKid

    60 Hz line frequecy divided to 1 pps

    your response makes me wonder - is this your own design, or did you get it from somewhere? The 4013 is doing pulse shaping, but the 4017 has a Schmitt trigger clock input, so it can do its own cleanup. Of much more concern is the apparent 160 V amplitude of the clock signal. Any thoughts on...
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