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  1. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    Kevin, Positive feedback doesn't reduce an opamp's gain, unless its resistance is so low that it overloads the opamps output. With positive feedback, the opamp's output will switch as close to rail-to-rail as it can. An opamp doesn't need a collector resistor because its output is push-pull...
  2. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    Kevin, No, an opamp will not be a linear amplifier when using positive feedback instead of negative. It will be a Schmitt trigger and produce a square-wave output. Its input will have hysteresis that is determined by the ratio of the feedback resistors. An opamp with negative feedback has its...
  3. audioguru2

    IR Remote Control Tester

    Xenobius, For an LED voltmeter, use an LM3914 chip, its datasheet is here: http://www.national.com/ds/LM/LM3914.pdf
  4. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    Who is wrong? We are talking about range (distance) here, which requires the use of a high-gain LINEAR amplifier in the receiver. The author probably knew that his project has a range problem when he mentioned using a high-powered IR LED to get more range. This project has a tone-modulated IR...
  5. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    Here's another one who believes that an input resistor is important in an opamp circuit: http://sound.westhost.com/dwopa.htm
  6. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    You didn't comment on my University Opamp Tutorial, which explained that BOTH inputs should have a voltage reference. My University is well respected, and so is National Semiconductor. In the latter's Application Note #20, An Applications Guide For Opamps, page 2 describes "The Non-inverting...
  7. audioguru2

    New Articles added

    Mixos, Thanks for the new good articles.
  8. audioguru2

    BCD counter

    Kevin, Are you using a 4017 chip? Both Texas Instruments and Fairchild call it a "Decade Counter/Divider". Try a 4060 binary counter with built-in oscillator, and listen to its octave-divided outputs. But it is a "ripple" counter, so you can't easily gate-decode its outputs, and some outputs...
  9. audioguru2

    Supa Dupa Basic Timed Latched Relay

    Laet, Your circuit will not work with the relay at the emitter of the transistor because the circuit is like a see-saw: As the current in the relay coil (transistor's emitter current) increases, then the current in the 25K resistor (transistor's base current) decreases: 1) The moment that you...
  10. audioguru2

    inverter oscillator

    Kevin, You're welcome. I'm glad that you understand the operation of this oscillator now.
  11. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    35 posts because of only one missing resistor?
  12. audioguru2

    decoding a 10khz tone!

    Qasim, If each person has a carrier frequency transmitter that is nearly the same, what is to prevent your receiver from picking-up interference between them? Your receiver will produce an interference beat frequency until it captures the strongest one. Also, FM receivers do not "mix" the audio...
  13. audioguru2

    Supa Dupa Basic Timed Latched Relay

    Laet, If the cars have a 13V terminal that is live only when the ignition switch is in the "engine running" position, hookup the relay there. Many cars have DRLs that way. Will that be OK?
  14. audioguru2

    inverter oscillator

    When the last circuit is re-drawn, look at what it is. It is a CMOS "classic" 2-inverter oscillator!
  15. audioguru2

    inverter oscillator

    Kevin, Is this your circuit? It doesn't need a pull-up resistor, especially not at an inverter's output. Inv 2 will self-bias itself near mid-supply, and in turn, will also bias Inv 1. So both inverters become high gain linear amplifiers, with positive feedback sustaining oscillation as the...
  16. audioguru2

    decoding a 10khz tone!

    National discontinued their LM567 more than 8 years ago. I think that Philips (the inventer) is still making their NE567.
  17. audioguru2

    inverter oscillator

    Right. I had a standard CMOS 2-inverter oscillator running at 1.6MHz (4049 buffer or HC territory) using only a 27pF cap and a multi-turn trimpot to calibrate its frequency. It never failed and never varied more than 1 percent. That's stable! They say that lower frequency CMOS oscillators are...
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Ante, Heh, heh, What do you call it that flows into jolly good "accumulators"? Doesn't the same thing flow out during discharge? But I have learned that when it is stored in there, it gets a new name.
  19. audioguru2

    inverter oscillator

    MP, The Fairchild application note does NOT say that a CMOS two-inverter oscillator is unstable. It simply says that a two-inverter oscillator will "fail to start" if its capacitor becomes disconnected. It says that the ONLY advantage of using a three-inverter oscillator is that it will...
  20. audioguru2

    inverter oscillator

    Kevin, Why don't you use a stable and popular, 2 inverter "Classic CMOS Oscillator"? I described its operation in the other post, here: http://www.electronics-lab.com/forum/index.php?board=15;action=display;threadid=883 R1 is optional since it makes the output frequency easier to calculate, and...
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