The weekly report discusses work on a product design by the Fueng Company engineering team. It focuses on the LM339 comparator device, which consists of four independent voltage comparators that can operate over a wide range of voltages and temperatures. The report examines the device's strong points of being easy to use and able to operate over a wide military temperature range. It also notes a weak point that it requires a single power supply. The next week's job will be to combine circuits.

1. [INC 281 MULTIDISCIPLINARY WORKSHOP WEEKLY REPORT] March 21, 2012
Name-Surname Pongsathorn Chumroenratanakorn
Student ID. 53211820
Group Name Fueng Company
Engineering Team Kwang, Nook, Opor, Fam, Will, Pieak, Nueng, Art
Members
Product Design Mohr, Pin, Nut, Mint, Pump
Team Members
Weekly Progress
LM339, these devices consist of four independent voltage comparators that are designed to
operate from a single power supply over a wide range of voltages. Operation from dual supplies
also is possible, as long as the difference between the two supplies is 2 V to 36 V, and VCC is at
least 1.5 V more positive than the input common-mode voltage. Current drain is independent of
the supply voltage. The outputs can be connected to other open-collector outputs to achieve
wired-AND relationships.
The LM139 and LM139A are characterized for operation over the full military temperature
range of –55°C to 125°C. The LM239 is characterized for operation from –25°C to 125°C.
Hysteresis is designed into most comparators, usually with a value of 5mV to 10mV. Internal
hysteresis helps the comparator avoid oscillation due to small amounts of parasitic feedback.
Though sufficient to prevent the comparator from self-oscillating, such internal hysteresis can
easily be swamped by any external noise of greater amplitude. In that case, you can improve
performance by adding hysteresis externally.
Figure 1. Pin of
LM339
Figure 2. A simple circuit with hysteresis
Engineering Analysis
Strong Point
- Easy to use.
- LM 339 operation over the full military temperature range of –55°C to 125°C.
- Can to use many operate.
Weak Point
- It is a single power supply.
Next Week Job
I will combine circuits.
Department of Control System and Instrumentation Engineering
KING MONGKUT’s UNIVERSITY OF TECHNOLOGY THONBURI