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Type: Posts; User: Audioguru

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    Closed: Re: BJT V(ce) ON in common emitter mode

    Don't you trust the datasheets? They guarantee that ANY transistor that has an hFE high enough to pass will saturate at the spec'd low saturation voltage. Then the base current MUST be 1/10th the...
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    Closed: Re: BJT V(ce) ON in common emitter mode

    No. The op is using the transistor as a common-emitter saturated switch and does not know that hFE is not used for a saturated transistor.
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    Closed: Re: BJT V(ce) ON in common emitter mode

    Of course you can have a common-emitter transistor saturate with its Vce much less than its Vbe. it is called "saturation".

    - - - Updated - - -


    The input transistor of a darlington transistor...
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    Closed: Re: BJT V(ce) ON in common emitter mode

    hFE is measured when the transistor is linear with plenty of Vce voltage and not saturated.
    Your transistor is a saturated switch and like most little transistors its datasheet says it saturates...
  5. Closed: Re: Problem with Logitech Audio PCB (No Sound Output)

    Your 18.22V power supply voltage is too high for those ICs.
  6. Closed: Re: Problem with Logitech Audio PCB (No Sound Output)

    The datasheet for the CD6282CS says its absolute maximum allowed power supply voltage is 15V or 16V so your 18V might blow them up.
    I did not see your photos because Imgur is still asleep.
    Why are...
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    Closed: Re: Power Amplifier Design

    When you said Power Amplifier Design I thought it would drive an 8 ohms speaker.
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    Closed: Re: Forward voltage of blue 3 mm led

    3.7V is the "storage voltage" when the Lithium Ion battery cell is half discharged or half-charged. You are lucky that the blue LED did not instantly burn out. A wall power supply that is only 3.6V...
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    Closed: Re: Forward voltage of blue 3 mm led

    What is the voltage of the 18650 battery cell while it is lighting the LED?
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    Closed: Re: Forward voltage of blue 3 mm led

    The forward voltage of a little blue LED is about from 2.6V to 3.6V at 20mA. Each one will have a different forward voltage, but most will "typically" be 2.8V.
    An 18650 Lithium Ion cell is 4.2V when...
  11. Closed: Re: Problem with Logitech Audio PCB (No Sound Output)

    When the IC was damaged by being connected backwards then maybe it damaged a part of the power supply. Measure the power supply voltage to see if it is normal or bad.
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    [SOLVED]Closed: Re: 12 vdc led running very hot

    It is NOT a 12V LED, It is an LED with a resistor that is designed for a 9V power supply voltage. It is overloaded when powered from 12V. At 9V then the small resistor and LED will not get too hot....
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    Closed: Re: Isolate R37 from Equation

    R37 is a very important part of the circuit since it and R42 set the input voltage of the opamp, then since the opamp has a gain of 1 the output voltage of the opamp is also set to be the same as the...
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    [SOLVED]Closed: Re: dc current gain variations

    A transistor in operation heats or cools which affects its hFE.
    A transistor in operation has a variable current which also affects its hFE.
    Design a transistor circuit with enough base current so...
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    Closed: Re: Rebuild low end computer speakers

    Many stereo sound systems are made with a ported woofer called a "sub-woofer" and two satellite speakers. Some of them sound pretty good. A midrange speaker is not needed if the tweeter can do it....
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    Closed: Re: Rebuild low end computer speakers

    The cheap little speakers have a single driver that is only 3.5" in diameter so it produces no bass and a very uneven high end. Each speaker amplifier is only 3.5W so the loudness is only a little...
  17. Closed: Re: Problem with Logitech Audio PCB (No Sound Output)

    The CD6282CS ICs are the power amplifiers that drive the speakers with a few Watts. If you connected their pins backwards or connected the polarity backwards of the power supply then they will get...
  18. Closed: Re: Replaced NiMh battery in small solar light

    The solar panel for a garden light usually has 4 solar cells, each producing about 0.5V with no load. They charge the battery all day at a low current to about 1.4V when fully charged.
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    Closed: Re: What dc can u measure?

    Today on one of the other websites he posted a second very simple question in German.
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    Closed: Re: What dc can u measure?

    This same German (?) circuit is on two or more other websites today.
  21. Closed: Re: [Moved] FM Transmitter with Single Transistor

    The transistor oscillator produces FM caused by the transistor capacitance changes which is the radio frequency changing up and down by the audio voltage swing. But the battery voltage running down...
  22. Closed: Re: [Moved] FM Transmitter with Single Transistor

    The mic is an electret type, not a simple condenser type that needs a 48V supply and an impedance converter.
    The simplicity of this transmitter causes performance problems and it has errors that...
  23. Closed: Re: Amplifier with 50khz frequency and 1 A output

    Maybe your multimeter cannot accurately measure currents above 1kHz? Maybe your power supply cannot provide enough power for all the heating?

    You call your schematic "audamp" but audio amplifiers...
  24. Closed: Re: HELP with Schematics for magnet launcher

    On the other websites you said you know nothing about electronics.
    The video has no part numbers so how do you know if you have suitable parts? Your parts might blow up and injure you or cause your...
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    [SOLVED]Closed: Re: whats hfe during peak current

    The maximum allowed collector current of an old 2N3055 transistor is 15A. They guarantee that it saturates not too bad with a collector current of 4A when its base current is 400mA (1/10th). They...
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