Observations and ConclusionsAns 1) Following are the results for circuit 1 measured during the lab.

Part 1 DC (Bias) circuit VBVEVC

7.514 V6.86 V10.37 V

Table 1: DC Voltages

IBIEIC

01.46 mA1.403 mA

Table 2: DC Currentsgmrer

149.556.12 mS17.12 2.672 K

Table 3: small signal AC ParametersThe values measured during the lab were very much close and equal to the values obtained in the pre-lab. The difference is only up to the decimal places that can be considered negligible. This minute difference can be due to physical conditions, such as temperature, resistance of breadboard and slightly different bias voltages. Therefore we can conclude that there were no discrepancies between pre-lab analysis and experiment.

Ans 2) Common Emitter amplifier (CE). (Note: Table 5 and 6 are results of Multisim Simulation)

Part 2 Common-Emitter (CE) Amplifier vi( dB)vo(dB)Av (dB)Av (V/V)

-42-141112.2

Table 4 - CE Amplifier Voltage GainFormulae used for calculating Ro and Ri: Rt-invtviRi

2.2 K3.536 mV2.02 mV2.9 K

Table 5 - CE Amplifier Input ResistanceRt-outAvovivo (with-load)Ro

3.3 K281.33 mV143.236 mV3.18 K

Table 6 - CE Amplifier Output ResistanceAmplifier performance strongly depends on bias current and temperature, therefore experimental results were slightly different from the pre-lab values but the main purpose of amplification was achieved.a) Notable deviations were observed in the values of Av and Ri. But the value of Ro is close to that of pre-lab. But as expected the CE amplifier provided a gain of 112.2 as compared to the pre-lab calculation of -139.9. Negative sign simply shows 180 phase shift. Pre-lab calculations were based on ideal assumptions such as capacitors short circuit for AC signal, making RE = 0 by shorting emitter to ground. Here, gain is inversely proportional to RE. RE = 0 means maximum gain, that is the case for pre-lab. Experimentally the biasing capacitor in parallel with RE tries to reduce the effect of RE to zero but it cant be ideally zero as capacitors have some impedance (Xc=1/wC) that depends on the frequency. Therefore experimental Av is smaller than Av in pre-lab. Ri calculated from experiment was found to be greater than the value of Ri calculated in pre-lab. That can also be due to the impedance of capacitors. Other reasons for deviations can be a result of physical conditions such as transistor parameters depends on thermal voltage, which depends on temperature directly. Early effects also bring the voltage gain down, which was ignored during pre-lab.

b) Io = vo/Rt-out = 143.236/3.3 = 0.0434 mAIi = (vt - vi)/Rt-in = (3.536-2.02)/2.2 = 0.689 uAAi = io/ii = 0.0434/0.000689 = 62.98Ap = Av Ai = 112.2 x 62.98 = 7067

Ans 3) Common Base amplifier (CB). (Note: Table 8 and 9 are results of Multisim Simulation)

Part 3 Common-Base (CB) Amplifier vi( dB)vo(dB)Av (dB)Av (V/V)

-355.6540.65107.7

Table 7 - CB Amplifier Voltage GainRt-invtviRi

17.53 3.536 mV2.205 mV29

Table 8 - CB Amplifier Input Resistance

Rt-outAvovivo (with-load)Ro

3.3 K285.02 mV144.38 mV3.214 K

Table 9 - CB Amplifier Output ResistanceAmplifier performance strongly depends on bias current and temperature, therefore experimental results were slightly different from the pre-lab values but the main purpose of amplification was achieved.

a) Notable deviations were observed in the values of Av and Ri. But the value of Ro is close to that of pre-lab. But as expected the CB amplifier provided a gain of 107.7 as compared to the pre-lab calculation of 139.9. Pre-lab calculations were based on ideal assumptions such as capacitors short circuit for AC signal. But practically capacitors have some impedance (Xc=1/wC) that depends on the frequency. Early effects bring the gain down and due to the fact that it was ignored in pre-lab, the pre-lab gain was slightly large.Ri calculated from experiment was found to be greater than the value of Ri calculated in pre-lab. That can also be due to the impedance of capacitors used. Other reasons for deviations can be a result of physical conditions such as transistor parameters depends on thermal voltage, which depends on temperature directly.

b) Io = vo/Rt-out = 144.38/3.3 = 0.0437 mAIi = (vt - vi)/Rt-in = (3.536-2.205)/17.53 = 0.076 mAAi = io/ii = 0.0437/0.076 = 0.575Ap = Av Ai = 107.7 x 0.575 = 61.9

Ans 4) Common Collector amplifier (CC). (Note: Table 11 and 12 are results of Multisim Simulation)

Part 4 Common-Collector (CC) Amplifier vi( dB)vo(dB)Av (dB)Av (V/V)

-7.19-7.18-0.010.998

Table 10 - CC Amplifier Voltage GainRt-invtviRi

13.134 K3.536 mV0.905 mV4.52 K

Table 11 - CC Amplifier Input ResistanceRt-outAvovivo (with-load)Ro

17.86 1.768 mV0.402 mV60.68

Table 12 - CC Amplifier Output ResistanceThere was a slight difference between the values but the main purpose of approximately unit amplification (Av = 1) was achieved.a) Notable deviations were observed in the values of Ri and Ro. But the value of Av was equal to that of pre-lab. But as expected the CC amplifier provided a gain of almost 1 as compared to the pre-lab calculation of 139.9. Pre-lab calculations were based on ideal assumptions such as capacitors short circuit for AC signal. But practically capacitors have some impedance (Xc=1/wC) that depends on the frequency of AC signal. For different frequencies we can have different values of Ro and Ri.Ri calculated from experiment was found to be greater than the value of Ri calculated in pre-lab. Whereas Ro calculated from experiment was smaller than that of pre-lab. This is due to the reason that Avovi is slightly larger than unity. This can also be due to the impedance of capacitors used. Other reasons for deviations can be a result of physical conditions such as transistor parameters depends on thermal voltage, which depends on temperature directly.

b) Io = vo/Rt-out = 0.402/17.86 = 0.0225 mAIi = (vt - vi)/Rt-in = (3.536-0.905)/13.134 = 0.2 uAAi = io/ii = 0.0225/0.0002 = 112.5Ap = Av Ai = 0.998 x 112.5 = 112.275

Ans 5) Common Emitter (CE) Amplifier has a high voltage gain but the output signal is inverted. The input resistance and output resistance are medium when compared to the other two. That makes it a good amplifier device. Current gain is large and power gain is very high. One of its uses is to amplify faint signals such as radio frequency signals.

Common Base (CB) Amplifier also has a high voltage gain. The input resistance is very small and the output resistance is medium. The voltage gain is almost independent of , which is desirable. They are not used alone as voltage amplifiers but combined with other configurations and they are good for high frequency applications.Common Collector (CC) Amplifier has a gain of approximately one. The input resistance is very large (much larger than load) and output resistance is small. Its voltage gain is almost 1 and its current gain is large. It is used as a voltage buffer which basically transfers a voltage signal from one circuit (with high output resistance) to the next circuit (with low input resistance) without losing the signal strength.

Ans 6) The purpose of capacitors is to filter AC signals from DC biasing parameters. DC signal are required to set the mode of operation, Q-point of the BJT. Once the biasing conditions are set, the ac signal is superimposed on the DC signal. Capacitors are open circuit for DC signals hence biasing is not effected by capacitors. For instance in the case of Common Emitter (CE) amplifier the voltage gain is inversely proportional to RE, the bypass capacitor will short the Emitter to the ground making RE meaningless or zero in other words. Hence increasing the voltage gain.