Laboratory 5 Daniel Choi 904169062 Section 2A 4 9 a We build the circuit using a diode a voltage source a lamp and a resistor such as the following We ran the power supply with 5V We turned the base current on and off by pulling one end of the resistor 4 211 V 4 211 mA 1 k The voltage across V CE 0 315 V We also measured I c 129 mA To calculate we used I B and I C I C I B I 129 mA min C 30 63 mA I B 4 211 mA We saw that our measured I C min I B because we had a 5V as our rail The rail capped out the out of the breadboard We measured V B 4 211 V R 1 k and I B current that was going through the lamp The transistor was saturated and had more current than it needs When running in saturation we measured V BC to be 0 31 When we switch to on Power is P I V BC 5 6 b We build the following circuit We explored the crossover distortion as we drove our circuit with a 1kHz sine wave with amplitude of 6V We see that the output is not as good the output of the single transistor circuit we built in section 4 3 because we are using a Class B amplifier as opposed to a Class A amplifier Class B amplifiers are significantly more efficient than class A amplifiers However Class B amplifiers have the problem of cross over distortion This occurs because the class B amplifiers only conduct half of the output at a given time 180 degrees and 180 degrees while class A amplifiers conducts all the time 360 degrees c We build the circuit below using a JFET We connect the 10k resistor to the 5V and then to the 0V and we compare the results When we put our gate to 5V the diode turns off When we ground it 0V the diode turns on We need the 270 resistor because we don t want to short our circuit Instead of connecting the 10k resistor to the 5V we touched the 5V power supply with our finger and the gate with our other hand When we touch our finger to the 5V supply the LED became dimmer Our body was capable of completing the circuit but it became dimmer than before because our bodies have certain impedance The input impedance is a bit higher than the impedance of our bodies When we vary the gate voltage we see that the light turns on at around 2 1V When we unplug the 10k resistor the LED turns off When we bring our hand close to the LED it turns on and when we bring our hand away it turns off 8 1 d We build the circuit as below We used a DVM to observe the output voltage of our potentiometer When we turn the potentiometer all the way to the left the voltage is 13 94V When all the way to the right it becomes 14 34V We couldn t get our voltage to 0V because the potentiometer is not sensitive enough for us to fine tune it to 0 volts We didn t get a gain of 200V mV as a typical 411 would have but the behavior was consistent 8 2 e We set up our circuit as the following diagram We run the circuit with a 1kHz sine wave with amplitude 1V We see that the gain was about 10V and that the maximum output swing was about 3 6V When we bump up the amplitude on our function generator we see that the graphs change and clip dramatically We then ran the function generator with a triangle wave and we saw that the graph was linear When we increase the frequency the amplifying properties of our circuit begin to break down At low frequencies the amplifier works fine We see this on the following graphs The first diagram below is a sine wave with low frequency and the second one is with high frequency We see that the second one begins to look more like a triangle wave at higher frequencies low freq high freq We then drove the circuit with a sine wave at 1kHz and we added a 1k resistor in series with the input Before we added the resistor we measured that V out 30 V After adding the resistor we saw that V out 15 4 V This is about a 50 drop in voltage and using the Thevenin equivalence we see that the input impedance is 1k f Using a 1V amplitude sine wave we increased the frequency We measured that our f 3 dB was 4 83MHz and this is when we see our output voltage is 70 7 of our input This frequency is also the bandwidth of our amplifier g When we use the 741op amp we find the 70 7 point to be 530kHz The lower than the first op amp we had previously used 8 3 We build a non inverting amplifier as the diagram below We see the following graph on our scope after building the circuit f 3 dB of this slower model is