The Using of Circut Board - Assignment Example

Lab Analog Electronic A circuit board also referred to as printed circuit boards are thin plates that contains electronic componentsoften found in communication and electrical devices. These plates provide the allowance for the circuit components to be able to transfer signals and information to each other and to the external devices. Printed circuit boards are practically applied in many devices. These include cell phones, televisions, computers, and other related communication devices. Their common function in such devices is to mechanically and electrically connect and support the electronic components through the use of conductive tracks and pathways. This experiment is centrally centered on TRANSISTOR FEEDBACK CIRCUITS board. Since the TRANSISTOR FEEDBACK CIRCUITs circuit boards has 4 circuit blocks, this experiment will explore all the four circuit blocks. The four include SERIES FEEDBACK or SHUNT FEEDBACK circuits’ block, the MULTISTAGE SHUNT SERIES FEEDBACK circuits block, the MULTISTAGE SERIES SHUNT FEEDBACK circuits block, and the DIFFERENTIAL AMPLIFIER circuits block. In regard to this, the experiment is set to achieve one key object, which is locating and identifying the key circuit blocks along the TRANSISTOR FEEDBACK CIRCUITS circuit boards. In order to realize this key objective there are other objective the experiment has to realize. First, at the end of the experiment, one is expected to have gained the ability to set up and activate circuit blocks through the two-post connectors, as well have the ability to apply power. Secondly, he or she needs to be able to describe how a series feedback circuit works when using the measurements of both the alternating and direct current. Thirdly, the experiment is set to help the student realize the ability to observe the effects of the series negative feedback on bandwidth when using a typical series feedback circuit. Understanding the effects of the shunt negative feedback upon the output and input impedance when a given typical shunt feedback circuit is applied should also be achieved. One other aim would be that the learner should be able observe effects of the shunt negative feedback upon the output and input impedance when using the typical shunt feedback circuit. After completing this experiment, the learner, is also expected to understand the operation, as well as the characteristics of two types of multistage feedback amplifiers. This should be done using direct and alternating current measurements. Last but not least, the learner needs to be able to calculate, as well as measure the gain in the shunt-series current with the help of a typical shunt-series multistage amplifier circuit. Equipment used in the Experiment The following are the set of apparatus that were used in this experimental set. They include F.A.C.E.T. base unit, the sine wave Multimeter Oscilloscope, the TRANSISTOR FEEDBACK CIRCUITS circuit board and the dual trace Generator. Experimental Procedures This experimental set up was segmented basing on the four TRANSISTOR FEEDBACK CIRCUITs circuit boards listed above. The diagram below represents circuits for the transistor feedback. The Circuits of Transistor Feedback (91008), (1999) Discussion In this section, it was found out through observation that the TRANSISTOR FEEDBACK CIRCUITS circuit board often has four common forms of feedback. First, there is the SERIES FEEDBACK also referred to as the SHUNT FEEDBACK. The series feedback is a shunt and Series feedback that is contained in any single. Secondly, it was observed that on the circuit of a transistor, there is the MULTISTAGE SERIES SHUNT FEEDBACK, as well as the MULTISTAGE SHUNT SERIES FEEDBACK. This multistage circuit contains two stages of amplifications. In essence, it often uses the combination of both series and shunt feedback. Thirdly, on the circuits of a transistor, there is the DIFFERENTIAL AMPLIFIER. In regard to this, the differential amplifier contains two transistors that are in a circuit and are used for amplification of small signals. Current feedback operation amplifier commonly referred to as CFA or CFOA is an electronic amplifier consisting of an inverting input that is quite sensitive to current, as opposed to voltage in the conventional voltage feedback operation amplifier. In some simpler configurations, like in linear amplifiers, a current feedback operation amplifier can be used to replace VFA without any circuit design needed. A four-resistor differential amplifier configuration, as well works using a CFA. The set shows the schematic diagram of a CFB amplifier. DISCUSSION In this experiment it was found that the SERIES FEEDBACK or the SHUNT FEEDBACK circuit block often develops shunt and series feedback in the amplifier circuit. In this case, the feedback is always in parallel or shunted with the amplifier input. UNIT 2 – SERIES FEEDBACK The effect of the Feedback on an AC Gain Block Diagram for the Feedback Amplifier Operation (Eric, 2004) Procedure The negative feedback amplifier or feedback amplifier is the amplifier that combines the input with certain fraction of the output such that the negative feedback opposes the previous original signal. In this case, the applied negative feedback causes an improvement in performance or gain stability, frequency response, as well as linearly, and in the effect reduce sensitivity to the parameter variations that are due to the environment or manufacturing. As illustrated in the diagram, the negative feedback amplifier is composed of three elements. These includes an amplifier that has gain AOL, the attenuating feedback network having a constant β < 1, alongside a summing circuit that often acts as a subtractor as shown in the block diagram above. In order to achieve a negative feedback, the procedure followed is outlined as First, the voltage supplied was adjusted to a value of 10+Vdc, Secondly, the R3 voltage was adjusted to a value of 5.5Vdc, the H1 was then connected to CH1and Vb to Vo. This was followed by setting the generator to 3Vpp , and 10 KHz sine wave output. What followed was to remove the C2 feedback Jumper, Basing on this procedure Vb= 0.25 Vpp , thus From the calculation to be Discussion Amplifier Operation without Feedback The Procedure was as follow first, the voltage supply was set at 10+Vdc, R3 voltage was adjusted to a value of 5.5Vdc then CH1was linked to CH1&Vb to Vo,. It was then that the generator was set at 3Vpp 10 KHz sine wave output. Basing on this readings were as follow Vo = 3 Vpp and Vb = 22m Vpp hence In this regard, the common emitter type amplifier having none bypassed emitter resistor is often used in demonstrating the series feedback, which is known to be the common type of negative feedback. More often than not, a negative feedback leads to the reduction in gain of the given amplifier upon which it is applied. Assuming there is increased base current emanating from the positive-going input signal, most certainly, the voltage that is at the emitter becomes more positively effective enough to cause a reduction in the base signal by an amount that is equal. A large capacitor placed across an emitter resistor would effectively bypass a positively going input signal to ground in such a way that there is no reduction in the base signal does occur. The value of the feedback factor (β) is often found from emitter resistor (RE) values, as well as from the values of the collector resistor (RC). In order to get a negative feedback, the value of the feedback factor (β) has to be a negative. Conclusion It was found that the negative feedback causes a reduction in the circuit gain. Exercise 2 In this exercise, the Effect of Feedback upon the Bandwidth was investigated. The diagram below shows the outline. Procedure The Amplifier bandwidth was first defined. The upper and lower cuts off frequencies were specified at 3 dB having been reduced from the midrange level. The squire wave input signals, as well as the formula fx = 0.159/T were used to approximate the bandwidth. It was found that negative feedback increases the bandwidth and reduces the gain in the amplifier. Exercise 3 In this exercise the effect of Feedback upon the Impedance was investigated. DISCUSSION The simple input impedance is defined as the sum of all series elements alongside the transistor base input impedances including the effects of all the bias resistors. From this exercise, it was found out that adding the series negative feedback onto a common emitter amplifier causes an increase in the input impedance as shown VR1 = Vi – Vb, Ii = VR1/R1 and Zi = Vi/Ii UNIT 3 SHUNT FEEDBACK In this exercise, it was found out that a small positive change in the value of Vi of the transistor causes an increase in the base current. This in turn, causes a decrease in collector voltage Vc. It was found out that a certain portion of the decreasing collector voltage gets sent back to, and is summed with the input signal that is rising. On the overall, the positive-going voltage Vi, as well as the opposite-in-phase Vc is said to oppose each other. As if not enough, it was found out that the gain in the feedback (Af) of the shunt feedback amplifier, is on approximation equal to the ratio of feedback resistor (Rf) to that of the series input resistor shown as Ri: Af = Rf/Ri. As for the shunt feedback, it was found out that the feedback ratio (β) is a reciprocal of Af: β = Ri/Rf. Exercise 2 Effect of Feedback on Bandwidth The diagram below illustrates the effects of Feedback on Bandwidth (Francos, 2003). It is common knowledge that a Bandwidth is what defines the input frequency breadth for which its output amplitude does remain constant, in the prescribed limits. Limits, in this case, are often defined to be the upper and the lower cut-off frequencies. The cut-off frequencies happens where the amplifier gain drops to the 3 dB of its mean gain, whereas, the average gain is used to refer to the midrange gain, which is the gain that is at the centre of the bandwidth. In certain some instances, a squire wave helps in measuring bandwidth of the amplifier. This it does through confirming some the squire wave characteristics at the amplifier output. According to what is observed on the oscilloscope, the time taken by the leading edge of the squire wave to reach 63 per cent of its own final level is referred to as the lower cut-off frequency. He simplified equation for the lower cut off frequency if (f1) or f2 = 0.159/T Exercise 3 Effect of Feedback on Impedance It is common knowledge that a Bandwidth is what defines the input frequency breadth for which its output amplitude does remain constant, in the prescribed limits. Limits, in this case, are often defined to be the upper and the lower cut-off frequencies (Francos, 2002). The cut-off frequencies happens where the amplifier gain drops to the 3 dB of its mean gain, whereas, the average gain is used to refer to the midrange gain, which is the gain that is at the centre of the bandwidth. In certain some instances, a squire wave helps in measuring bandwidth of the amplifier (Francos, 2002). This it does through confirming some the squire wave characteristics at the amplifier output. According to what is observed on the oscilloscope, the time taken by the leading edge of the squire wave to reach 63 per cent of its own final level is referred to as the lower cut-off frequency. He simplified equation for the lower cut off frequency if (f1) or f2 = 0.159/T In conclusion a shunt-series FB is often identified through noticing how the feedback develops. Occasionally, the shunt-series FB is often connected in shunt with an input stage, as well as in series with the output stage. It is noticed that the current gain always is higher compared to the voltage gain in the shunt series FB Amplifiers. What determines the current gain is the ratio of the shunt feedback resistant denoted as R5th to the series FB resistor often denote as Ref. UNIT 4 – MULTISTAGE AMPLIFIER FEEDBACK Exercise 1 Shunt-Series Current Gain DISCUSSION In this exercise current gain, which is at time referred to as the current amplifier, equals the ratio of the shunt resistance (Rsh) to the series resistor (Ref). Exercise 2 In this exercise involved Shunt-Series Output Impedance DISCUSSION In this exercise it was found out that the circuit output impedance (Zo) is equal to the transistor collector impedance that is in parallel with a collector resistor. This thus implies that Zo = (Rco x Rc)/(Rco + Rc). This is due to the circuit, high output impedance that often acts an instant current source for the small load. Exercise 3 Series-Shunt Voltage Gain (Eric, 2004). In this exercise, it was found that in the multistage amplifier having series-shunt feedback resistor Ref does provide series feedback. Moreover, the Rsh provided a shunt feedback to the input stage. It was also ascertained from the exercise that the circuit voltage gain relates directly to Rsh as shown Av = Rsh/Ref and that the series-shunt feedback amplifier often has high voltage gain. CONCLUSION In conclusion, the voltage gain changes whenever the FB resistors ratio changes. It was true as well that the voltage gain is equal to the ratio of the series resistor and the shunt resistor. It was also found to be true the fact that the output collector resistor has no effect on the voltage gain. References Erik, B. (2004). Current Feedback Amplifiers. New York: Oxford Publishers. Francos, S. (2002). Design with Operational Amplifier and Analog Integrated Circuit. McGraw-Hill. p. 293. Francos, S. (2003). Design with Operational Amplifier & Analog Integrated Circuit. McGraw-Hill. p. 299. Transistor Feedback Circuits (1999). Electricity and Electronics. Retrieved on 16th Sept 2012. Read More