help with circuit evaluation

Discussion in 'General Electronics Chat' started by donut, May 23, 2012.

  1. donut

    Thread Starter Member

    May 23, 2012
    Learning to understand circuit design of attached file.

    Please tell me how values of bypass caps c6 and c7 were derived?

    Please help me understand how values of R4 L1 and L2 were derived?

    Please tell me what the 10 ohm resistor r3 is doing in the circuit.

    Thanks for the help
  2. Col


    Apr 19, 2012
    1) At 2.4GHz the 15nF capacitor is almost a short to ground, so any coupling of the RF signal should be removed from VCC.

    2) I'm not going to cruch the numbers here but I assume this is a matching circuit to ensure maximum coupling of your RF signal to your microstrip. IE matching device output impedance to line impedance. Google impedance matching. R4 is separate, this is bais for the device output amplifier

    3) I think R3 is adding to the decoupling effect of the surrounding caps. It forms a low pass RC filter on the power line. Down side is it will burn some power

    In general, for a basic understanding consider all your L and C elements as impedance at the RF frequency.