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参数资料
| 型号： | LA1245 |
| 元件分类： | 接收器 |
| 英文描述： | AUDIO SINGLE CHIP RECEIVER, PDIP20 |
| 封装： | 0.300 INCH, DIP-20 |
| 文件页数： | 8/12页 |
| 文件大小： | 712K |
| 代理商： | LA1245 |
LA1245
No. 737-5/12
Notes on LA1245 usage
1. When suddenly tuned to a broadcasting station of intermediate or high field strength, a large current of high
frequency flows into the signal meter circuit, causing the local oscillator malfunctions and abnormal noises.
To eliminate this :
Use R208 ≥ 240Ω for manual tuning type.
Use R208 ≥ 80Ω, and use the local oscillation coil at the 1/3 tap (except SW) for electronic tuning type (which uses
a narrow band filter).
2. Use the bias on the condition RF VCC ≤ IF VCC, since abnormal noise levels might be caused when detuning a
strong input on the condition RF VCC > IF VCC.
3. Use the signal meter driving output (VSM) at VSM ≤ VCC–2 (V) to avoid saturation caused by VCC.
4. Use 1/2 or more tap of LW and MW oscillation coil to improve S/N and the detuning characteristics of the
distortion ratio.
5. Use the full-tap of SW oscillation coil, to allow the sag in oscillation power by the decreasing of Q.
6. Avoid the coupling of the antenna tuning circuit and the local oscillating circuit so as not to leak the local oscillation
into the antenna tuning circuit.
7. Connect the detection capacitor C113 between pin 13 (output) and pin 14 (VCC) to avoid the leakage of the IF
signal into the GND line. Connection between pin 13 and pin 12 (GND) increases the tweet interference and
deteriorates the usable sensitivity.
Moreover, depending on the positions of C113 and the bar antenna, higher harmonics having twice or three times
the frequency of the IF signal may pass into the antenna and cause tweet interference, and in extreme cases
oscillation might be cause. To prevent this :
Shorter lead wires and connect them near 13 and 14 pins.
Place C113 far from the antenna.
8. When a cable or something similar is connected to a local oscillation buffer (pin 20), which is equivalent to
connecting a capacitor of about 20pF, the output from the buffer will be of sawtooth waves, causing the level low at
the short wave band. To prevent this, connect a resistor between pin 20 and GND, which will increase the operating
current of the buffer amplifier. Since the maximum current obtained from pin 20 is 2mA, the suitable resistance
between pin 20 and GND is 1.5k
Ω.
9. Use a semi-fixed resistor for R211 to allow the fluctuation of VSM.
10. When changing an IFT or using an RF tuner, select a filter and related circuits according to the following conditions.
The input levels of each terminal where 30% modulated detection output of
25dBm is obtained are as follows :
Pin 11 input
when Rg = 520
Ω (470Ω + 50Ω)
75dB
μ
Pin 9 input
when Rg = 50
Ω
53dB
μ
Pin 6 input
when Rg = 50
Ω
48dB
μ
Pin 3 input
when Rg = 50
Ω
22dB
μ
Slight change in IFT, however, will be covered by changing the constant of resistors R202 and R204.
11. When the coupling coefficient of the local oscillation coil is small and an anti-resonance point of about 100MHz is
present or the stray capacitance between pin 19 and pin 20 is large, the buffer output (pin 20) may be subject to
parasitic oscillation of about 100MHz. In this case, connect a capacitor of about 30pF between pin 20 and GND. To
observe parasitic oscillation, connect a capacitor of 5pF in series with the probe. If the probe is connected direct to
pin 20, the input capacitance of the probe causes parasitic oscillation to stop, which makes it impossible to observe.
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相关代理商/技术参数 |
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|---|---|
| LA1247 | 制造商:SANYO 制造商全称:Sanyo Semicon Device 功能描述:AM ELECTRONIC TUNER |
| LA12540 | 制造商:LIGITEK 制造商全称:LIGITEK electronics co., ltd. 功能描述:ROUND TYPE LED LAMPS |
| LA12540-PF-TBF-X | 制造商:LIGITEK 制造商全称:LIGITEK electronics co., ltd. 功能描述:TAPE AND BOX TYPE LED LAMPS |
| LA1256 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Octal Peripheral Driver |
| LA125P | 制造商:LEM 制造商全称:LEM 功能描述:CURRENT TRANSDUCER LA 125-P |
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