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  • Ten Daily Electronic Common Sense-Section 144

    What is the temperature difference potential?

    The electric field hinders the further diffusion of electrons. When dynamic equilibrium is reached, a corresponding potential difference is generated at both ends of the conductor. This potential difference is called thermoelectric potential.

    The difference between an op amp and a comparator:

    An op amp is exactly the same as a comparator. Simply put, a comparator is an open-loop application of an op amp. However, the design of the comparator is used for voltage threshold comparison, and the required comparison threshold is accurate. The rising or falling time of the output edge after comparison is shorter, and the output conforms to TTL/CMOS level/or OC, etc. The accuracy of the intermediate link is not required, and the driving ability is also different.
    General situation: using op amps as comparators, most of them cannot reach the full-scale output, or the edge time after comparison is too long, so it is better to use less op amps as comparators in the design.
    The difference between op amps and comparators Although comparators and op amps have the same symbols on the circuit diagram, the two devices are indeed very different. Generally not interchangeable, the difference is as follows:

    1. The flipping speed of the comparator is fast, about on the order of ns, while the flipping speed of the op amp is generally on the order of us (except for special high-speed op amps).
    2. The op amp can be connected to a negative feedback circuit, but the comparator cannot use negative feedback. Although the comparator also has two input terminals, non-inverting and inverting, there is no phase compensation circuit inside it. Therefore, if negative feedback is connected, the circuit cannot work stably. There is no internal phase compensation circuit, which is the main reason why the comparator is much faster than the op amp.
    3. The output stage of the operational amplifier generally adopts a push-pull circuit with bipolar output. Most comparator output stages are open-collector structures, so pull-up resistors are required. Unipolar output, easy to connect with digital circuits.

    What are the features of the VIC module in the LPC2000 series ARM?

    1. ARM PrimeCell vector interrupt controller;
    2. Up to 32 interrupt request inputs;
    3. 16 vector IRQ interrupts;
    4. 16 priorities, which can be dynamically assigned;
    5. Can generate software interrupts.

    What is a complex PLD programming logic device?

    CPLD is an array-type density PLD device developed from PAL and GAL. It has a large scale and can replace dozens or even hundreds of general-purpose ICs.
    CPLD mostly adopts programming technologies such as CMOS, EPROM, EEPROM and Flash memory, and has the characteristics of high density, high speed and low power consumption.

    What is the file system structure of SCOS?

    1. SCOS has two layers of files MF and EF. Since it is dedicated to one card, the DF file is no longer set.
    2. There are three internal basic files of SC()S: SF for storing passwords, KF for storing keys, and AF for storing system information. The internal basic files are only accessible by COS and adopt a transparent structure.
    3. There are three basic working files of SCOS: a PF for storing balances, an RF for storing transaction records, and an IF for storing personal information. Among them, PF and IF adopt a transparent structure, and RF adopts a ring structure with fixed-length records.
    4. SCOS accesses the file with a unique identifier (2 bytes).
    5. The EF file consists of two parts: the file header and the file body. SCOS adopts the method of storing the file header and the file body separately and facing each other, that is, the file headers are gathered together. And start storing from the minimum address (0000) of E2PROM. The file body is also put together and stored from the largest address of E2PROM. This arrangement facilitates the addition of new documents.

    What is the development trend of EDA technology?

    Facing today’s rapidly developing electronic product market, designers need more practical and efficient EDA tools. Use a unified integrated design environment to change the traditional design thinking. Concentrate on design conception, scheme comparison and finding optimal design. It is necessary to develop electronic products with excellent performance and first-class quality at the fastest speed. So higher requirements are put forward for EDA technology.
    Future EDA technology will achieve new breakthroughs in simulation, timing analysis, integrated circuit automatic testing, high-speed printed circuit board design and expansion of development and operating platforms. Towards powerful, easy to learn, easy to use the direction of development.

    What are the participants in the communication network in the M2M technology framework?

    Network operators and network integrators.

    What are the components of the microphone input?

    1. Microphone preamplifier
    2. Single microphone application
    3. Dual microphone application
    4. Microphone bias circuit
    5. Microphone current detection
    6. Microphone programmable gain amplifier

    What ports are there on the camera interface?

    The camera interface has 4 DMA ports, and memory scaling DMA (Mem0ry Scaling DMA, MSDMA) input is used for image preview port.
    The memory scaling DMA input is used for the video codec port, and the preview output port (Preview out port, P-port) and video codec port (Codec out port, C-port) are used for their respective AHB buses. The four DMA ports are independent.

    What is the role of the collision sensor?

    The function is to detect the signal of the collision intensity of the car when the car collides. And input the signal to the airbag ECU.
    The airbag ECU judges whether to detonate the gas generator to inflate the airbag according to the signal sent by the collision sensor.


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