lab5 - Experiment-5 Experiment-5 Feedback Circuits and...

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Experiment-5 R. B. Darling EE-332 Laboratory Handbook Page E5.1 Experiment-5 Feedback Circuits and Other Applications Introduction The objectives of this experiment are to examine the characteristics of several feedback amplifier configurations. Voltage regulators are a rudimentary form of feedback amplifier where the input signal is a DC reference voltage which gets current amplified and passed onward to the load. These are examined first, followed by feedback circuits for short-circuit protection, class-AB output booster stages, and sinewave oscillators. In addition to the performance measurements, you should also pay attention to how the biasing of each amplifier stage is achieved, how the signal is coupled from stage to stage, and what design strategy has been adopted to desensitize the circuit performance to variations in the transistor parameters. For each circuit in this experiment, try to answer the question: “What has been achieved by connecting the transistors in this configuration?” To begin to answer this question, first identify whether a particular transistor is providing bias stabilization for other transistors, or is a gain stage in the signal path. Some transistors may simultaneously function in both roles. Then try to determine what components set the voltage gain of the circuit. Track the path of the signal through the different stages of the circuit and try to understand how much voltage gain is produced across each stage, how big the signal is at each node along the path, and what limits the signal swing at each node. For each circuit that uses feedback, you should be able to follow a closed path through the circuit corresponding to the feedback loop. Draw a schematic of the amplifier in your lab notebook and mark it up extensively to show the DC bias voltage at each node, the path that the signal takes from input to output, any feedback loops, and any thing else that is of interest to you. The feedback circuits described in this experiment are not as simple as those previously used in this lab. While all of the component values are fairly close to the values needed to make the circuits work, normal variations in transistor parameters will require that each circuit be “tuned-up” slightly to center the signal swings or trim out the gain. This is left for you to do without any explicit instructions and is intended to force you to understand how the circuits work and to gain skill in electronic troubleshooting. Similarly, the procedures will only ask you to measure certain performance parameters without giving explicit instructions.
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Experiment-5 R. B. Darling EE-332 Laboratory Handbook Page E5.2 Procedure 1 Series-pass zener diode positive voltage regulator Comment The purpose of a voltage regulator is to maintain a constant output voltage across an arbitrary load, independent of the current that is drawn by the load, and independent of the input supply voltage. The
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lab5 - Experiment-5 Experiment-5 Feedback Circuits and...

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