Part A: Switching regulator design exercise

Theoretical design
This design is entirely theoretical. You will not be expected to assemble the circuit and test it.

Collect information
Data on the TL497AI switching voltage regulator is provided from the Texas Instruments 1989 Linear circuits data book, volume 3, pages 2-135 to 2-141. From this data assemble the following:

- a table showing
- allowable input voltage range
- allowable output voltage range
- V ref (typical)
- switching transistor maximum current
- diode maximum current
- A sketch of the power dissipation rating curve.

Design
Using this data and the typical application data (use the basic configuration even if current values fall slightly outside the specified range), design a regulator to meet the specifications below. Include component ratings in your design and choose the inductor core, wire size and number of turns. Your design should also include thermal considerations by estimating the heat loss. If necessary, specify heat sink thermal resistance.

Specifications:

Type of regulator : Step down Input voltage Vi : 24
Output voltage Vo : +5V
Output current Io : 300 mA
Maximum output ripple Vr : 50 mv
Ambient temperature Ta : 50 deg C

Report
Present a report containing the following:

- assembled data
- design calculations, including inductor core choice/details
- a circuit sketch using the same schematic layout as in the data, and showing all component values including ratings.

Part B: Logarithmic amplifier design

Design
Given any of the following transistor arrays, find the collector current versus base-emitter voltage characteristic of the transistors from the data sheet which follows. Typical figures are acceptable. Note that it is logarithmic over two decades of current:

LM or CA 3045, 3046 or 3086.
All of these are similar electrically. All are in
14 pin DIL packages and contain five similar transistors.

Design a logarithmic amplifier of the two-transistor type described in the Study Book based on this device and LM108 op. amps. whose characteristic is to approximate the relationship:

Vout = -5 log (2Vin/2Vref)
as closely as possible at room temperature, over a two decade range of Vin from 0.1V to 10V. Arrange for Vout to always be > 0V. Data for the LM108 is attached. Use to +/- 15 volt supplies.

Test (Optional)
Assemble the circuit. Spurious oscillation will probably occur causing incorrect operation and will need to be suppressed with capacitors such as fairly large values (4.7 µF or more) from the output to ground. Do not forget to use compensation capacitors on the 308 according to the data sheet. If necessary, extra large values may help stop oscillation.
Measure the characteristics of your amplifier using a digital multimeter over its allowed range of input voltages at room temperature.

Note: If you do not succeed in getting this circuit to work, it may be because of spurious oscillations which are very common. The use of an oscilloscope would help to identify and thus avoid these oscillations. However if you do not have access to an oscilloscope, try adding capacitance in other places or contact the lecturer for advice.

Report
- Show all design calculations
- Show full circuit diagram with all component values
- Results from testing or simulation
- Comparison of results with specifications with observations and conclusions.

Part C: Electronic integrated circuits ICs
Select two ICs and submit a short report for each, covering the following details:

- what the IC is (name, type)
- explanation of the IC's features and how it works
- sample circuit application making use of its feature(s) with a circuit operation explanation (include any relevant calculations).