LM386N

TIGER ELECTRONIC CO.,LTD L ow Voltage Audio Power Amplifier L M 386 N/D DESCRIPTION T he L M 386 is a power amplifier designed for u se in low voltage consum er applications. The gain i s internally s et to 20 to keep external part count l ow, but the addition of an external resistor and c apacitor between pins 1 and 8 will increase the g ain to any v alue from 2 0 to 200. T he inputs are ground referenced while the o utput autom a tically b iases to one-half the supply v oltage. T he q uiescent p ower d rain i s o nly 2 4 m illiwatts when operating from a 6 v olt supply , m a king the D386 ideal for battery o peration. O utline Drawing LM386N DIP8 LM386D F EAT URE B attery o peration M i n i mu m e x t e r n a l p a r t s W ide supply v oltage range: 4V–12V L ow quiescent current drain: 4m A V oltage g ains f rom 2 0 t o 2 00 A vailable in 8 pin DIP package SOP8 APPLICATION AM-FM radio amplifiers P ortable tape player am plifiers I ntercom s T V sound sy stem s L ine drivers U ltrasonic drivers S m all servo drivers P ower converters P IN CONFIGURATION 1/6 LM386N/D E QUIVA LENT SCHEMATIC A ND CONNECTION DIAGRAMS A BSOLUTE MAXIMUM RATINGS ( Ta=25 ° C) Characteristic M axim u m I nput Vo ltage S upply Vo ltage M axim u m P ower Disspation S oldering tem p erature(10 sec.) Junction Te m p erature Operating Te m p erature S t orage Te m p erature SOP8 D IP8 Symbol VIN V cc PD TS Tj Ta m b Ts tg Va l u e ± 0.4 15 660 1200 260 1 50 - 10~+70 - 40~125 Unit V V mW °C °C °C °C E LECTRICAL C HARACTERISTICS ( Unless otherwise specified: V cc=6V , R L =8 Ω , f =1kHz , Ta m b =25 ℃ ) Characteristics Operating Supply Voltage Quiescent Current Output Power Voltage Gain Bandwidth Total Harmonic Distortion Power Supply Rejection Ratio Input Resistance Input Bias Current Te s t c o n d i t i o n s V cc=6V ， V I N =0 V cc=6V, R L =8 Ω ， THD=10% V cc=9V, R L =8 Ω ， THD=10% V cc=6V, f=1kHz 1 0 μ Ffrom P in 1 to 8 V cc=6V ， P ins 1 and 8 open V cc=6V ， R L =8 Ω ， Po=125mW ， f=1kHz P ins 1 and 8 open V cc=6V ， f=1kHz ， C B Y P A S S =1 0 μ Pins 1 and 8 open referred to O utput V cc=6V ， Pins 2 and 3 open S y m bol Vcc Icc Po Av BW THD Min 250 500 - Ty p 4 325 700 26 46 300 0.2 M ax 12 8 U nit V mA mW - dB kHz % PSRR RIN IB - 50 50 250 - dB kΩ nA 2/6 LM386N/D A PPLICATION H INTS G AIN CONTROL T o make the L M 386 a more versatile amplifier, two pins (1and 8) are provided for gain control. With pins 1 and 8 open the 1.35 kW resistor sets the gain at 20 (26 dB). If a capacitoris put from pin 1 to 8, bypassing the 1.35 kW resistor, the gain will go up to 200 (46 dB). If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200. Gain control can also be done by capacitively coupling a resistor (or FET) from pin 1 to ground. A dditional external components can be placed in parallel with the internal feedback resistors to tailor the gain and frequency response for individual applications. For example, w e can compensate poor speaker bass response by frequency shaping the feedback path. This is done with a series RC from pin 1 to 5 (paralleling the internal 15 kW resistor). F or 6 dB effective bass boost: R . 15 kW, the lowest value for good stable operation is R = 10 kW if pin 8 is open. If pins 1 and 8 are bypassed then R as low as 2 kW can be used. T his restriction is because the amplifier is only compensated for closed-loop gains greater than 9. I NPUT BIASING T he schematic shows that both inputs are biased to ground with a 50 kW resistor. The base current of the input transistors is about 250 nA, so the inputs are at about 12.5 mV w hen left open. If the dc source resistance driving the D386 is higher than 250 kW it will contribute very little additional offset (about 2.5 mV at the input, 50 mV at the output). If the dc source resistance is less than 10 kW, then shorting the unused input to ground will keep the offset low (about 2.5 mV at the input, 50 mV at the output). For dc source resistances between these values we can eliminate excess offset by putting a resistor from the unused input to ground, equal in value to the dc source resistance. Of course all offset problems are eliminated if the input is capacitively coupled. W hen using the L M 386 with higher gains (bypassing the 1.35 kW resistor between pins 1 and 8) it is necessary to bypass the unused input, preventing degradation of gain and p ossible instabilities. This is done with a 0.1 µF capacitor or a short to ground depending on the dc source resistance on the driven input. 3/6 LM386N/D A PPLICAT ION CIRCUIT Vs 6 2 Vin 10K 3 + 4 1 8 LM386 7 0.05uF 10 5 250uF Vin 2 6 Vs 1 - 10u 8 5 250u 0.05u 10 LM386 3 + 4 7 BYPASS 10K F ig1 Am plifier w ith G ain = 2 0 (Minimum Parts) Fig2 Am plifier w ith G ain = 2 00 Vs 6 2 Vin 10K + 4 1.2K 1 8 10uF 250uF 220 热敏电阻 2 6 - Vs 1 10uF 390 8 5 250uF ＬＭ386 Vo LM386 3 旁路 5 3 + 4 7 0.05uF ÅÔ· 10 RL 7 0.05uF 10 4.7K 0.01uF F ig3 Am plifier w ith G ain = 5 0 Fig4 Low D istortion P ower W ienbridge Oscillator Vs 6 2 Vin 7 - 6 Vs 1 30K 8 50uF 5 RL 旁路 0.1uF 2 - 0.033uF LM386 3 + 4 8 1 5 250uF Vo 3 + 4 LM386 7 Vo 10K 0.05uF 10 RL 1K 10K 10K F ig5 A m plifier w ith B ass B oost Fig6 Square W ave O scillator 4/6 LM386N/D Vs 0.05uF 10K 2 2200pF Cc 6 1 10uF Vin VoL 10K 8 LM386 LM386 铁氧体线圈 250uF 5 47 0.05uF 3 + 4 7 10uF 8 喇叭 Fig7 AM Radio Power Amplifier T YPICAL P ERFORMANCE CHARACTERISTICS 5/6 LM386N/D 6/6