Explore BrainMass

Explore BrainMass

    BJT suitability of transistor types simple circuit

    Not what you're looking for? Search our solutions OR ask your own Custom question.

    This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

    Determine the most suitable transistor from TABLE B for use in the circuit of FIGURE 3. You may assume in all cases that the transistor is biased with VBE = 0.6 V. Justify your choice in detail.

    © BrainMass Inc. brainmass.com December 16, 2022, 1:41 pm ad1c9bdddf


    Solution Preview

    Determine Quiescence or Q point voltages and currents at set points in the circuit.

    The Q point biasing points are determined by
    Considering DC conditions so ignore (remove for analysis) any capacitors in the circuit
    Considering that no input is present and biasing set by the voltage divider at the input
    The circuit is thus redrawn to represent this scenario

    The Q point base voltage V_BQ is thus obtained as the voltage appearing across
    the voltage divider formed by 22 kΩ and 2.7 kΩ resistors across the supply, thus


    Assuming a base emitter voltage V_BE=0.6V we can then determine the Q point
    of the emitter voltage, V_BQ from


    We can now determine the Q point currents, initially the emitter current, i_EQ
    that flows from Ohm's Law

    i_EQ=V_EQ/R_E =2/100=20mA

    We assume the BJT transistor draws very little base current (a good
    simplification as it has a very high input resistance when connected in
    common emitter configuration which is the case). Then we can determine the
    Q point collector current, ...

    Solution Summary

    Choosing a transistor type based on biasing of circuit, power requirements and power handling, collector current are examined.