Audio AGC amplifier circuit schematic
As shown in the figure is an audio AGC amplifier circuit. The dynamic range of this amplifier is greater than 50dB. The distortion of the output waveform is very small, and it has the advantages of fast startup and slow attenuation. Circuit input 40 ~ 20mV and output 0 ~ 1.2V adjustable level, single power supply, power consumption current is less than 1mA (5V voltage). VT2 and VT4 are P-channel JEFT. It forms an equivalent resistance voltage divider with R2, R3 and R4 (R10, R11 and R12), which is connected to the input circuit. When the input level is lower than 40mV (peak-to-peak value), the input is equally distributed between R2 and R3, R4, and the output amplitude of A1 is not large enough to turn on the positive peak detector VT2. Pull the gate of the junction field effect transistor to + 5V to pinch off its channel and produce a very high resistance from the drain to the source. When the peak-to-peak value of the input voltage is higher than 40mV, VT1 turns on at the positive peak of A1 output, reducing the gate-to-source voltage of the junction field effect transistor. The channel resistance is used to reduce and attenuate the input signal to keep the peak-to-peak value of the Al output voltage at about 1.2V. 
High definition Led Display refers to the screen with pixel density above p2.5, which can display clearer content at a closer distance. It is widely used in some high-end meetings, monitoring facilities, airport signs and other places.
The high-definition display screen has higher technical requirements.
1. Packaging technology. Because more lamps are arranged in limited space, the requirements for lamp beads are higher and higher, and the lamp beads are smaller and smaller. Now there are 21211515.1010.0909, etc. on the market. In order to achieve a more stable effect, the new packaging process cob packaging, directly packaging three chips into PCB, so as to achieve the purpose of more intensive lamp beads and clearer picture, the biggest advantage of this process is stability.
2. Patch technology: small lamp beads shall be welded on the PCB, which requires more accurate placement machine and solder paste machine to ensure error control.
3. After the installation process and products come out, the installation workers must receive special training to ensure the levelness and damage in the installation process.
Features of LED high clear screen:
1. As the name implies, high-definition display screen is in the same space, with high resolution and easy to reach 4K resolution. Vision display company currently has p0.9, p1.25, p1.56, p1.667, p1.875, p1.98, etc.
2. In order to ensure the flatness of the screen body, die-casting aluminum box is widely used. In this way, in addition to ensuring the levelness, there is no need for fans, and the heat dissipation is guaranteed.
3. The Vision display company has launched a single high-definition LED display, which is ultra light and ultra-thin and can be used for home theater, TV broadcast, etc.
4. Compared with the traditional monitoring monitor, LCD screen is used more, but the inherent defects such as stitching and low brightness can not be improved. The small high-definition spacing just makes up for these shortcomings, so it is widely used in the monitoring field.
5. Vision display has done a lot of investment and research and development in HD. In addition to the general HD display, there are dual data and dual power HD displays. When one power supply or signal has problems, the other signal or power supply is automatically connected to work. It effectively guarantees the use of high-end meetings or places where no mistakes can occur.
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