NAME: ____________________________________

The thermal voltage, V_t, is given by kT/q where:

• k is Boltzmann's constant and equals 1.3807x10^-23 joules/kelvin
• T is the absolute temperature in kelvins (0K = -273.15^oC).
• q is the electronic charge of 1.602 x 10^-19 coulomb

1) At what temperature is the thermal voltage actually equal to the 25mV that we generally use when working problems.

2) What is the basic functional relationship between the collector current in a BJT transistor and the base-emitter voltage?

3) The transconductance of a BJT transistor is the ratio of the changes in what two parameters? Derive the equation which expresses the transconductance of a transistor in terms of its DC operating point values.

4) There is a Rule of Thumb that states that the collector current of a BJT will increase by an order of magnitude for every 60mV increase in the base-emitter voltage. Derive this relationship. At what temperature is this Rule of Thumb actually true? What is the actual change in voltage needed to obtain an order of magnitude increase in current?