EE 321L Analog Electronics Laboratory Fall 2010Lab 8BJT Single-Stage AmplifiersIn this lab you will build a linear single-stage amplifier and measure transistor amplifierinput and output resistances.Pre-Lab1. Design the circuit in step 1. Compute rπand re.2. Compute the input resistance for step 3 and the frequency to use.3. Compute the theoretical gain in step 3.4. Pick a resistor value for step 4.5. Determine the expected output resistance in step 6.6. Compute the theoretical emitter follower gain in step 9.7. Compute the t heoretical output resistances in section 9, use it to pick a source resis-tance for step 10, and compute the output resistance for step 10.A Linear BJT Common-Emitter AmplifierIn this section we will look at how gain can be traded f or linearity in the common-emitteramplifier. You get the highest g ain by applying the input voltage directly to the base. Butin that case linearity is poor because base voltage and collector current are related throughan exponential. If on the other hand the input is coupled through a large resistor to thebase the base end of the resistor becomes a virtual ground and the effect is that the sourcevoltage effectively controls the base current. The base current is linearly related to thecollector current and thus we expect better linearity. Because the source now has high outputresistance the cost of this linearity is reduced gain from source voltage to collector voltage.1. Build the common-emitter amplifier pictured below. Make IC= 1 mA, VC= 10 V, andVE= 5 V with VCC= 15 V and VEE= 0 V. Choose R1and R2small enough that t hevoltage divider is no t affected much by the base current (about 10 times more currentthrough the voltage divider than into the base).1EE 321L Analog Electronics Laboratory Fall 2010R12RERCVCCVEER2. Connect the function generator through a large capacitor to the input and apply asmall signal of sufficiently high frequency that it is not attenuated by the RinC filter(verify that the gain is independent of frequency near the frequency you pick).3. Measure the signal gain and compare to a theoretical prediction. Plot the input/outputcharacteristic in XY mode allowing it t o saturate at the ends. Except for the saturatedportions, is it very linear?4. Next insert a resistor (source output resistance) between the function generator andthe coupling capacitor. Make the resistor much larger than the input resistance(R1||R2||rπ). Estimate the gain vc/vs. Compute vb/vs, then ib/vs(ibis through rπonly), then ic/vs, and finally vc/vs.5. Apply a input signal, measure the gain, and compare to your prediction. Plot theinput/output characteristic in XY mode including saturation at the ends. Is it morelinear than before?Input and Output resistance of the Common-Emitter AmplifierIn this section you will measure the input and output resistance of the common-emitter am-plifier. The standard way to do that is to compare the voltage with no source/load resistanceto the voltage with some resistance. The reduced voltage with resistance is due to a voltagedivision.6. Compute the input and o utput resistances of the common-emitter amplifier, ignoringthe Early effect. Pick resistors of similar size.7. Measure the input resistance by measuring the output voltage (for a very small inputto ensure linearity) with and without the resistance attached to the input, and comparewith the theoretical prediction.8. Measure the output resistance by measuring the output voltage with a nd without theresistance attached to the output, and compare with the theoretical prediction.2EE 321L Analog Electronics Laboratory Fall 2010Output Resistance of the Emitter Follower AmplifierIn this section you will measure the output resistance of the emitter follower, whose input isthe base and output the emitter. The emitter follower is non-unilateral, which means thatthe output resistance depends on the source resistance.9. Using still the same circuit, couple the function generator through a capacitor to thebase, and the emitter through a capacitor to a scope probe. Measure t he small-signalgain and compare with a theoretical prediction.10. Connect the function generator directly to the base capacitor. Measure the outputresistance. Compare with a theoretical prediction.11. Now connect the function generator through a large resistor, large enough to change theoutput resistance. Measure the output resistance again and compare to the