A constant DC voltage is critical in many applications nowadays, but the voltage provided by many energy sources will vary with changes in load impedance. Furthermore, when an unregulated DC power supply is the energy source, its output voltage will also vary with changing input voltage. To circumvent this, some power supplies use a linear voltage regulator to maintain the output voltage at a steady value, independent of fluctuations in input voltage and load impedance.
a. Design a linear regulator with short-circuit protection capability. Explain in details the operation principle for your design.
b. Select the proper values for the components you used in your design. Then calculate the regulated voltage and also the maximum allowable current.
c. Verify you calculation with the circuit simulation in Proteus.
d. Discuss the advantages of the DC power supply over the batteries.
2. Op-amp is a widely-used component in analogue circuit design. One op-amp based circuit is shown below.
a. What is the function of the given circuit? Give an example where this circuit can be used in realistic application.
b. With the aid of diagram, explain in details the function of each op-amp configuration.
c. Assuming that the output of the op-amps can swing between 15V, choose appropriate (and realistic) component values in order to obtain the output in Vb with a fixed amplitude of 10V, and an adjustable frequency with a range of 100 Hz to 100 kHz.
d. Verify your design using simulation.
e. Draw voltage vs. time plot for va and vb with at least one full period of signal, when the variable resistor is set at 9.9 k.
3. Modern industrial process requires accurate temperature monitoring. In the following, a thermocouple is used as a sensor to measure the temperature. The chosen thermocouple exhibits linear relationship between input and output. It gives an e.m.f of 820 V when the hot junction is at 20C and the cold junction at 0C. In order for real-time display and data-logging, the measured temperature needs to be acquired by a micro-controller (C). This C allows to have the input from 0V to 5V. The frequency of the environment noise is higher than 10kHz.
a. Design an op-amp based circuit between the sensor and micro-controller including signal amplification and the noise filtering. Choose appropriate and realistic chips and components for your design.
b. Verify your designed circuit in the simulation.
c. If this thermocouple is replaced with a RTD, discuss the potential impact on the performance of this application.