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LM13700: LM13700

Part Number: LM13700

Tool/software:

Hi  Team,

I have come across a limiter circuit in a audio amplifier circuit. The circuit is not functioning when we overdrive the signal.I am attaching a schematic here. Could you explain how this circuit works? am not getting proper output

  • The input signalat U1.5 is 360mVrms AC along with the DC bias

  • Arjun,

    When the negative VOUT peak(s) get large enough to turn on Q1, The amount of current into pin 1 will increase the value of "X" in the equations on schematic. When X increases VOUT decreases and at some point C20 voltage falls or hold steady. 

    The LM13700 provides a signal that opposes VIN to reduce the VIN gain to keep negative peaks limit to a value (roughly 6V - 2V = 4V for Q1 on). Therefore, I wouldn't expect a 6V +/-1V single at output to engage limiting. 

  • Thanks Ron for your reply. Stil i have some doubts and i have also attached a ppt in which what i have understood and my observation on limiter circuit. I need your opinion too.... 1. What is the purpose of R12?

    2. The input to the limiter should be very low which is mentioned in the datasheet. But here voltage is high. So how the limiter ic will work?

    3.Role of R17 and c14?

    4.while simulating am not getting 6V atR22 instead am getting around 7.49 why?

    5. How i have to set the limitwr action

  • Arjun,

    The power point looks like TI_TINA simulation circuit, can you share it?

    1) R12 converts the output current of LM13700 into a voltage. R12 is the gain of the IOUT to VOUT conversion.

    2) R17 and R21 reduce the input voltage. (remember R12 increases the LM13700 output voltage)

    3) R17 is covered in point 2. C14 increases gain for high frequencies. starting at 160kHz.

    4) That's odd

    5) Ratio of R34, R35