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LM386 is very popular IC also in Japan. It is used in Radio receiver. The power of it (500mW) is enough for the personal use. But sometimes, the gain of it (40dB) is not enough. Especially the direct conversion receiver depend on all of its gain on the audio amplifier. And therefore, we must stay sometimes the pre-amplifier before LM386. I will show you the way to get the 74dB only with LM386. Please watch the circuit ! Rf is the feedback control resister. By chanbeing the Rf you can tune the gain of this circuit as follows.
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Rf (ohm)
Feed back
Resistor |
Gain
dB |
| 3.3 | 74 |
| 10 | 70 |
| 33 | 54 |
| 105 | 44 |
| 820 | 34 |
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