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| LA4285资料 | |
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LA4285 PDF Download |
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File Size : 116 KB
Manufacturer:SAN Description: The signal detectors sense and rectify the receiver and microphone signals to opposite polarities referenced to the internal reference voltage of approx. 2V.The voltage at RxDet will go positive and at TxDet negative in the presence of a signal at the respective channel input. In the idle(no signal) state, the voltages at RxDet, TxDet and CMP are equal to the internal reference voltage. Signal at Txin will result in an decreasing level at TxDetout and hence also at CMP input. the transmitter channel and decrease it in the receiver channel. Signal at Rxin will do vice versa. The voltages RxDetout and TxDetout controlthus the gain setting in respective channel through the comparators using the CMP input as a summing point with an input current of less than 1A. The attack time in the receiver channel is set by C2 together with C1 and either by the maximum current capability of the detector output or it with R2 added. The transmitter channel works likewise. See figure.5. The decay time in the receiver and transmitter channels is set by C2 and C3 respectively. The resistor in the time constant is formed by an internal 200kresistor in parallel with the external resistors R3 and R4 respectively. The influence of eventual R1 and R2 can be omitted. The text above describes the case when only one channel is open at a time and there is a distinctive pause between signals at receiver and transmitter channel inputs so the circuit will have time to reach its idle state. See figure.10 A) to E). If one of the channels gets an input signal immediately after the signal has disappeared from the other channel input the effective decay time , as the CMP input sees it, will be shorter than in the first case. See figure.10 F) to G). The capacitor C4 at CMP -input sets the speed of the gain change in the transmitter and receiver channels. The capacitors C2 and C3 should be dimensioned for a charging time of 0.5-10mS and for a discharge time of 150-300mS. The question of switching times being a highly subjective proposition, is in large dependent of the language being spoken in the system , caused by the varying sound pressure picture of the different languages. A hysteresis effect is achieved in the switching since the level detectors sense the signals after F2 and F5 respectively (F2 and F5 are affected by the gain setting). For example: If the transmitter channel is open (maximum gain),a smaller signal at Txin is enough to keep the channel open than would be necessary to open it when the receiver channel is open. The output swing of the level detectors is matched for variations in the supply voltage. The detectors have a logarithmic rectifier characteristic whereby gain and sensitivity is high at small signals. There is a break point in the curve at a level of + 200mV from the internal reference voltage app.2V,where the sensitivity for increasing input signals decreases with factor of 10, increasing the detectors dynamic range. See figure.8. |
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| 1PCS | 100PCS | 1K | 10K | ||
| 价 格 | |||||
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型 号：LA4285 厂 家：SAN 封 装： 批 号：6RX4/6Xr 数 量：430 说 明：Bid Price |
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运 费： 所在地： 新旧程度： |
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| 联系人：刘先生，罗小姐，刘小姐，刘先生，王先生 |
| 电 话：0086-755-83576094,83576097,83576087,83576084,83979425 |
| 手 机：0086-(0)13728684091 |
| QQ：2355773149,2355773142,61991728 |
| MSN：franlmk168@live.cn |
| 传 真：86-755-83576061 |
| EMail：sales@xgf-ic.com, kupan_ic@126.com |
| 公司地址： 深圳市龙岗区龙岗街道龙岗大道远洋新干线晶钻广场2栋B座2915房 |
