Daniel Choi 904169062 Laboratory 4 4 1 a We will get a 2N3904 NPN transistor and we will verify the leads We see that the middle one is the base We need to use a DVM to measure the voltage drop across the BC and BE junctions to correctly identify the collector and emitter sides of the transistor We get the diode drops to be 0 691V for one of the leads and 0 665V for the other The side with the slightly lower voltage drop is the collector 4 2 b We will build an emitter follower by setting up the circuit as following We will drive the circuit with a sine wave at 5kHz making sure that the dc offset on the function generator is set to zero We then change the amplitude 5V 8 5V We see that the first figure 5V looks similar to the half wave rectifier and the negative portions are truncated As we increase the amplitude we see that our small bumps begin to appear and get bigger but they never surpass the V When we bump the voltage too high on our function generator the transistor starts to break down and it does not work properly and these are where we see the bumps We will no connect the emitter to 15V instead of the ground and see the results The improvement that we see is that we see the positive and negative portions of the output voltage The output follows our input but with a slight offset c We will then measure the voltage across the collector and emitter measure it to be V CE 15 6 V V CE We use a DVM to find this and we 4 3 d We will build the circuit as the following a We will use a 4 7 F electrolytic capacitor and a 1k resistor and we will add it to our circuit We run the function generator with a sine wave with amplitude of 500mV We observe the results on our scope and we see that the input pk pk is 1 1V and the output pk pk is 1 06V We then go to the acquire menu and change the setting to average mode We then see that the input pk pk is 1 02V and the output pk pk is 980mV We need to use the blocking capacitor so that we can block out the dc while coupling the ac signal We now measure Z out by using V TH R R Z V 100 0 7 V 100 Z 1 02 V Z out 46 We will now unplug our blocking capacitor and we see that there is not much of a change With a large load we don t draw enough current to see a significant difference But b We remove our 1k load and we measure Z We use a 100k in series with out 10k load and we use the voltage divider ezuation We measure our V out to be 0 248V and V to be 0 508V V out 0 248 V 100 000 V 0 508 V 100 000 Z Z 104 838 7 e Using our DVM we measure our V CE to be 16 20V 4 4 f We build our circuit as the following We run the function generator using a 1kHz sine wave with an amplitude of 2V Comparing our V and V out we see that the graphs are quite similar but there is an offset on our V out The offset is about 8 00V We then raise the amplitude of our function generator to check the circuit s capability of generating output swings before clipping The maximum amplitude we can bring the function generator to before we start seeing clipping was about 6 65V We then max out the amplitude 10V of our function generator and we see that the clipping is somewhat symmetrical When the voltage at the base tries to climb above the power supply we see this clipping We see this better when we lower the volrage of our power supply to 6V We can definitely see that our V out does not surpass the V This shows that our circuit does not allow an amplitude that surpasses the voltage of our rail 2V 6 65V 10V g We plug in our voltmeter across the collector and emitter and we get a reading of h We build the following circuit We use different values of R and we measure the current B by the Resistance We then get our value by dividing V CE 8 85 V I C We find I B by dividing the Voltage across IC IB R IC VB IB 1 05M 953k 95 3k 9 53k 953 0 876mA 0 882mA 9 510mA 14 894mA 14 933mA 4 40V 4 39V 4 15V 2 90V 0 735V 4 19 A 4 607 A 43 55 A 304 A 771 2 A 209 1 191 4 218 37 48 99 19 36 4 7 i We build the following circuit We run the function generator and we get the following picture V and V out We use these to calculate the voltage gain We find that V 1 92 V V gain out 9 69 V 198 V We measure the We also see that our signal is inverted We then unplug the function generator and we see where the voltage rests the quiescent point We see that it sits at 8 40V This voltage is the state of our circuit when there is no input signal We take out output at the collector because our circuit is used as an amplifier We don t take it at the emitter because at that point there are no amplifying qualities there To find the output impedance we add another load to the circuit as following We measure V out 10 6 V V out R V R Z V 1 4 V Z 10 6 V 10 6 V 1000 100 0 4 975 k 1 4 V 1 4 V 4 8 h Using our DMM we find the impedance of our speaker We find it to be j We set up the circuit as following Z speaker 91 5 we simply plug in the NPN emitter onto our previous circuit We set the function generator to about 5kHz We hook up our circuit to the input and ground to check that it works properly We then hook the speaker to the output of the amplifier 1st transistor We barely hear the sound that the speaker emits We barely hear the sound because the current that runs through this transistor is very small We then hook the speaker up to the output of the emitter follower We hear a much louder noise We hear a higher sound because the resistor ratio shoots the current way higher x10 and the sound is amplified