Circuit Noiz Calculator

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Th3_uN1Qu3
    Believe in
    • Jul 2010
    • 6031
    • Romania

    #1

    Circuit Noiz Calculator

    Here's another spreadsheet by yours truly. If you have worked with operational amplifiers of any kind, or did any audio mixing, i'm sure you had a noise problem at least once. That hiss when dealing with low level signals. Tape hiss, radio hiss, microphone hiss... It's everywhere.

    Well, now you are able to know exactly how much noise your amplifier circuit makes. This spreadsheet takes your design parameters and calculates SNR (signal to noise ratio) for you. It gives a lot of insight and busts a lot of myths passed by word of mouth or by "common knowledge" on internet forums.

    For example i thought that the hiss common to microphone preamps is inherent, and it's because of the circuit gain. Indeed, when connecting a more sensitive mike, you can turn the gain down and the hiss goes away - but that's only because the more sensitive mike gives a higher input level! Even if you would have a more sensitive mixer or recorder or whatever to capture the signal of the weaker mic, so you wouldn't need as much gain in your amplifier, the hiss would still be the same! For the same input signal level, SNR stays constant regardless of gain. That is, unless the signal source you are amplifying happens to have a hiss of its own, but that's a different can of worms...

    Also, a lot of people say that the input and feedback resistors have to be as low in value as practical. As you will see, the noise source with the highest value dominates, and with common opamps like TL07x or NE553x, the highest noise source is the opamp itself, so the resistor values don't really matter unless you get into specialty opamps with really low self noise.

    Technical notes:
    • Supported configurations: Inverting and non-inverting opamps.
    • As usual, the input values are in blue and the results are in yellow. The nV/√Hz value for the opamp you can get from its datasheet.
    • Current noise is not calculated, this is negligible in most cases. It will be added sometime.


    More goodies coming soon, right now i need some sleep.
    Attached Files
    Originally posted by PeteS in CA
    Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
    A working TV? How boring!
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Circuit Noiz Calculator

    Resistor type is also important,
    due to Thermal Johnson Noise Generated by a Resistor.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment

    Related Topics

    Collapse

    • GraphicMan
      Pioneer A-205 faint noise/hiss issue
      by GraphicMan
      as the title says, i noticed a faint noise/hiss when there is nothing playing that i dont think i have had with this unit before ever, i have not changed its location
      what makes it more weird, this noise is gone almost completely if my hand gets within 5cm or less close to it (close to the panel)!!
      out of curiosity what does that mean?
      thanks
      05-19-2024, 11:45 AM
    • tony359
      Removing electrical noise introduced by fan
      by tony359
      Hi all,

      I am working on a sound processor, it tends to overheat so I fitted a fan inside. The fan is connected to the +15V of the PSU via a DC-DC converter based on the LM2596 to reduce the voltage to around 10.5V.

      Unfortunately the analogue circuitry is picking up the noise from the fan in two ways:
      1. The fan is close to the analogue section, the motor itself gets into the outputs so I'll have to move it somewhere else
      2. Even with the fan running outside of the case, there is still some noise which is clearly going back to the processor via power line....
      11-28-2023, 05:18 AM
    • MegaZAC
      Onkyo TX-SR805 noise in one channel
      by MegaZAC
      Surprisingly enough, this receiver doesn't have the DSP chip issue. The HDMI board does not get hot, and sound over HDMI works fine.

      Regardless of the input, the right channel has noise that is clearly noticeable even on average volume level. The only cases when there's no noise is when VCR input is selected (some tracks on the board are damaged, maybe that's why), or if HDMI input is selected but nothing plugged into it. In all other cases, even when no input is connected I still have the noise.

      There's some logic behind it. As soon as I select an input I get only left...
      04-23-2025, 10:09 PM
    • Astonished
      Fixing the Charge Circuit of the Batteries of the DC Motor
      by Astonished
      Hi friends of electronics

      What you see in the video and pictures attached is the circuit for charging the batteries of a DC motor.

      The problem is that this circuit cannot charge the batteries (3 1800mAH NiMH batteries) any more. When the circuit was OK, its green LEDs lit up one at a time to show that the batteries have charged more. But now that the circuit is flawed, LEDs light up as you see in the video and at the same time successive beeps are heard.

      Please help me fix this circuit.

      (the datasheet of the IC: https://pdf.datasheet.live/28...
      01-28-2025, 06:24 AM
    • rddube
      Lenovo L490 Ram voltage circuit malfunction
      by rddube
      Hello friends,

      Looking for some guidance here. The RAM voltage circuit on this motherboard keeps burning out PU301 which is a RT8231AGQW. Copy of the board with the burnt chip attached with some voltage measurements and copy of the schematics also included.

      I think I've checked almost every component in the circuit, but when I change the RT8231, the laptop starts I have 1.2V on the inductor for about 10 seconds and then the RT8231 goes south and no more voltage on the inductor. All other voltages on the laptop are good, this is the only one conking out for a reason I...
      07-15-2025, 04:41 PM
    • Loading...
    • No more items.
    Working...