Questions about Crystal oscillator circuit؟؟

Discussion in 'General Electronics Chat' started by samy555, Aug 27, 2015.

  1. samy555

    Thread Starter Active Member

    May 24, 2010
    I've download (using google) the TX-2B/RX-2B datasheets,

    Iwill focus on the crystal oscillator built around Q1:


    I have a toy car, the transmitter unit is working on 3 Volt. It's a replica for the circuit in the datasheets. Only difference in the values of the elements:


    For the last figure, the 40MHz crystal is connected between two different voltages; the 3V at the collector and the approx. 1.2V at the base. This voltage difference is making crystal to oscillate.

    Question1: Where this oscillating signal is fed, Is to base , collector or both?

    Question2: What is the function of C1? Is it doing a feedback from collector to Emitter?

    Question3: Is the above configuration a common emitter crystal oscillator?

    Question4: I built the circuit and measure the operating point (IC = 22mA, VCE = 2.5V), is this a good Q-point? 22mA be withdrawn from a 3V battery is a very big current. It will be voided battery quickly.

    Thank you for your patience to my many questions
    Last edited: Aug 27, 2015