Names __________________________ Date __________________________ Lab 6 – The Common-Emitter Amplifier Introduction The purpose of this experiment is to demonstrate the operational characteristics of a small signal common emitter amplifier with a 180 degree phase shift. The input is applied to the base and the output is measured from the collector. Parts Two 3.9 k Ω resistor 4.7 k Ω resistor 10 k Ω resistor 2.2 μF capacitors 100 μF capacitors 2N3904 NPN Transistor Procedure Wire up the following circuit: Be sure the signal generator is in ’50 Ohm’ mode. Biasing (dc) REGIME Calculate the base, collector, and emitter voltages with respect to ground. Now measure these voltages. How do your numbers compare? Beta for this transistor can be considered to be 120, and VA = 100V. Remember, in DC, the capacitors are large enough to be considered open circuits. Include your equations here: VB (calculated) = ________ V VB (measured) = ________ V VC (calculated) = ________ V VC (measured) = ________ V VE (calculated) = ________ V VE (measured) = ________ V Explain possible differences between the measured and calculated values: Small-signal (ac) REGIME How are the large caps to be considered as when in ac regime? Calculate the small signal parameters and draw the small signal circuit of the amplifier. Calculate the amplifier characteristics RIN, ROUT, Av, and output swing. Use your notes if needed. Now simultaneously measure vin and vout and record your results. What is your measured voltage gain? What about the phase shift? AV (measured) = __________ V/V Phase Inversion (Yes or No): ___________ Explain possible differences between measured and calculated gains: Now start increasing your input voltage until you see your output starting to look funky. At what output voltage does the upper half of your cycles look incorrect? How about the bottom half? What is going on here - why is it the transistor no longer working at those specific values? Explain the behavior of the circuit at those amplitudes and compare your results to the calculation of amplifier swing.