Swiss chipmaker STMicroelectronics NV reported a wider first-quarter loss Wednesday as sales sank across the board, and said it would lay off 1,200 people.
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And
Semiconductor manufacturer Atmel Corp. has cut another 293 jobs in the company’s second round of layoffs in five months.
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Touch sensing is fast becoming an alternative to traditional pushbutton switch user interfaces, because it requires no mechanical movement, and it enables a completely sealed and modern-looking design. Expanding beyond the consumer market, touch sensing is beginning to take hold in medical, industrial and automotive applications for reasons such as aesthetics, maintenance, cost and cleanliness.
Technologies
Mainstream technologies include capacitive sensing solutions and inductive sensing solutions. The available of the two provides designers more flexibility to choose the right touch technology for their application. So which one’s right?
Microchip’s mTouch™ Sensing Solution provides a free and easy method for designers to add touch sensing to applications utilizing PIC® microcontrollers without the cost of fee-based licensing and royalty agreements. Being a source-code solution further helps engineers quickly integrate touch sensing functionality with their existing application code in a single, standard microcontroller, thus reducing the total system cost associated with current solutions.
Capacitive and Inductive Touch Solutions:
Continued from CMOS vs. Bipolar Operational Amplifiers: Which is best for my application? Part I
Input Bias Current
Input bias current is the amount of current flow into the inputs of an amplifier to bias the input transistors and can range from peco-amperes to hundreds of nano-amperes. Amplifiers with a CMOS input stage generally have less bias current when compared to an amplifier with bipolar input transistors, typically around 1 pA, while bipolar transistors can be orders of magnitude higher. This bias current is converted into a voltage through the input resistance of the circuitry and will end up resulting in an error voltage at the output of the amplifier. Thus, the less bias current, the better.
Price/Packaging
CMOS is known as a more cost-effective technology. This is mainly due to lower wafer costs, driven by the high volume of CMOS logic chips. Despite the lower wafer costs, for a given current capability, CMOS transistors take up more silicon area then bipolar transistors. So even though the wafer costs may be lower, there are less die per wafer, thus negating the cost benefit. In the end, the cost structure of these two process technologies is very similar.
Leadless packages and chipscale packages are allowing smaller solutions but in the end a larger silicon area will limit packaging options.
The Best Choice
Bipolar amplifiers are grounded in history, but CMOS amplifiers offer some inherent advantages. BiCMOS processes are the relative newcomers to the field, but this hybrid technology takes the best of both worlds and provides superior performance at a price point that is becoming more and more competitive.
If the op amp interfaces with a high-impedance sensor such as a thermocouple with some passive filtering, then keeping bias currents to a minimum will be important. In this case, an amplifier with a CMOS input stage is the best choice. If the application requires a high-speed, high-slewing amplifier, then a bipolar amplifier may offer the best performance at the lowest quiescent current.
But in this economy, go with the cheapest!
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Op Amps
CMOS, bipolar or even BiCMOS are common process technologies used for the development of operational amplifiers, and each of these process technologies offers their own advantages and disadvantages when it comes to op amp design. Which one’s the best? That depends on the application of course!
Power Consumption
CMOS is known for lower power, as the transistors only draw current when switching states. But, as the bandwidth increases, a CMOS amplifier’s current increases exponentially, and soon draws more current then a comparable bipolar amplifier! Therefore, bipolars are typically better suited for high-bandwidth, high-slewing applications. For lower-bandwidth applications, CMOS amplifiers can still provide power advantages. For example, the MCP6041 low-power CMOS op amp has a quiescent current of only 600 nA, and provides a gain-bandwidth-product of 14 kHz.
Voltage Offset
Voltage offset is the amplifier’s voltage difference between the inverting and non-inverting inputs. This error is highly dependent upon how well matched the input transistors are. Bipolar transistors inherently offer better matching, resulting in lower offset voltages. Mismatch can be limited for any process by using laser trimming, fuses or even EPROM. Don’t forget that better matching also results in less voltage-offset drift over temperature.
Noise Performance
CMOS transistors have worse low-frequency noise (flicker noise or 1/f noise) than bipolar transistors. Here, noise is dominated by irregularities in the conduction path and noise due to the bias currents within the transistors. In a bipolar transistor, the conduction path is buried down inside the silicon unlike a CMOS transistor, where the current flow is near the surface, making it susceptible to defects in the surface of the silicon, which increases the low-frequency noise.
At higher frequencies, 1/f noise is negligible; white noise from dominates. CMOS transistors have a lower transconductance relative to similarly sized bipolar transistors, which results in higher broadband noise. In general, bipolar op amps hold an inherent advantage over CMOS when it comes to noise performance.
to be continued…
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Op Amps
MCP6041
CAN (Controller Area Network)
Many network protocols are described using the seven layer Open System Interconnection (OSI) model, as shown in Figure 1. The Controller Area Network (CAN) protocol defines the Data Link Layer and part of the Physical Layer in the OSI model. The remaining physical layer (and all of the higher layers) are not defined by the CAN specification. These other layers can either be defined by the system designer, or they can be implemented using existing non-proprietary Higher Layer Protocols (HLPs) and physical layers.
The Data Link Layer is defined by the CAN specification. The Logical Link Control (LLC) manages the overload control and notification, message filtering and recovery management functions. The Medium Access Control (MAC) performs the data encapsulation/decapsulation, error detection and control, bit stuffing/destuffing and the serialization and deserialization functions.
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CAN Design Solutions
Speaking of comparators, here are several reasons you should avoid using op amps as comparators:
• Op Amps are much slower than comparators
• Instability due to unintentional positive feedback
• Phase inversion issues
• Internal diodes causing havoc
Check out this informative post on Op amps as comparators by reader Ron Amundson:
…. if you are using bipolar power supplies for the op amps, and the op amp/comparator feeds a micro, you need to play a few games, and that will add some cost and real estate. Or perhaps you are able to run the op amp on a unipolar supply, and it has a rail to rail output, and you will use the same power supply for the micro… expect Mr Murphy to arrive, as you chase op amp instability due to unintentional positive feedback (mostly due to common mode effects). Such scenarios can be a real bear to deal with, requiring untold number of pcb revs to make things happy and stable… and what if the pcb gets dirty with age, throw in a little leakage to create a positive feedback path, and now you have field failures left and right….
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Comparators Product Family
Op Amp Product Family
Microchip Technology Inc., a leading provider of microcontroller and analog semiconductors, today announced the MCP6561/2/4/6/7/9 (MCP656X) family of high-speed (45 nS) comparators. With rail-to-rail input and output, low operating voltage down to 1.8V, low quiescent current and package options with push-pull and open-drain outputs, the new devices provide a high level of performance for a wide variety of applications. Read more in the Press Release
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Comparator Product Family
