TIGER ELECTRONIC CO.,LTD Low Voltage Audio Power Amplifier LM386N/D DESCRIPTION Outline Drawing The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200. LM386N The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 DIP8 milliwatts when operating from a 6 volt supply, making the D386 ideal for battery operation. LM386D FEATURE Battery operation Minimu m ex tern al p arts Wide supply voltage range: 4V–12V Low quiescent current drain: 4mA Voltage gains from 20 to 200 SOP8 Available in 8 pin DIP package APPLICATION PIN CONFIGURATION AM-FM rad io amp lifiers Portable tape player amplifiers Intercoms TV sound systems Line drivers Ultrasonic drivers Small servo drivers Power converters 1/6 LM386N/D EQUIVALENT SCHEMATIC AND CONNECTION DIAGRAMS ABSOLUTE MAXIMUM RATINGS (Ta=25 °C) Characteristic Maximum Input Vo ltage Supply Vo ltage Symbol VIN Vcc SOP8 DIP8 Maximum Power Disspation Soldering temp erature(10 sec.) Junction Temperature Operating Temperature Storage Temp erature Value ±0.4 15 660 1200 260 150 -10~+70 -40~125 PD TS Tj Tamb Tstg Unit V V mW °C °C °C °C ELECTRICAL CHARACTERISTICS (Unless otherwise specified: Vcc=6V , R L =8Ω , f=1kHz , Tamb =25℃ ) Characteristics Operating Supply Voltage Quiescent Current Output Power Voltage Gain Bandwidth Total Harmonic Distortion Power Supply Rejection Ratio Test conditions Min Typ Vcc Vcc=6V， V I N =0 Vcc=6V, R L =8Ω， THD=10% Vcc=9V, R L =8Ω， THD=10% Vcc=6V, f=1kHz 1 0 μ Ffrom Pin 1 to 8 Vcc=6V， Pins 1 and 8 open Vcc=6V， R L =8Ω ， Po=125mW ， f=1kHz Pins 1 and 8 open Vcc=6V， f=1kHz， C B Y PA S S =1 0μ Pins 1 and 8 open referred to Output Input Resistance Input Bias Current Symbol Vcc=6V， Pins 2 and 3 open Icc Max Unit 12 V mA 4 325 700 26 46 300 8 BW 2 50 5 00 - - kHz THD - 0.2 - % Po Av PSRR RIN IB mW 50 - 50 250 dB dB - kΩ nA 2/6 LM386N/D APPLICATION HINTS GAIN CONTROL To make the LM386 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. Additional external components can be placed in parallel with the internal feedback resistors to tailor the gain and frequency response for individual applications. For example, we 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). For 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. This restriction is because the amplifier is only compensated for closed-loop gains greater than 9. INPUT BIASING The 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 when 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. When using the LM386 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 possible 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 APPLICATION CIRCUIT Vs 6 - 2 Vin 8 5 250uF + 7 0.05uF 3 Fig1 2 Vin LM386 10K 6 Vs 1 - 1 4 Amplifier with Gain = 20 8 250u 5 LM386 10K 10 10u 3 BYPASS 4 Fig2 0.05u 10 7 + Amplifier with Gain = 200 (Minimu m Parts) 1.2K 6 4 Fig3 250uF 5 7 0.05uF + 390 8 5 ＬＭ386 LM386 3 10uF 1 - 8 Vin 10K 2 10uF 1 - 2 Vs 6 Vs 旁路 220 热敏电阻 3 7 0.05uF + 4 10 ÅÔ· 10 4.7K Amplifier with Gain = 50 Fig4 250uF Vo RL 0.01uF Low Distortion Power Wienbridge Oscillator Vs 6 - 0.1uF LM386 3 1 + 4 8 250uF 5 10 0.05uF Vin 10K 旁路 7 0.033uF 2 10K Fig5 Amplifier with Bass Boost 2 6 Vs - 1 30K 8 LM386 Vo 3 + 50uF Vo 5 7 RL 4 RL 1K Fig6 10K Square Wave Oscillator 4/6 LM386N/D Cc Vin VoL 10K Vs 0.05uF 6 10K 2 1 - 10uF 8 2200pF LM386 LM386 3 + 4 Fig 7 铁氧体线圈 250uF 5 7 10uF 47 0.05uF 8 喇叭 AM Rad io Po wer Amp lifier TYPICAL PERFORMANCE CHARACTERISTICS 5/6 LM386N/D 6/6