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IL386

Low Voltage Audio Power AMP

IK Semicon Co., Ltd 

IL386

ELECTRICAL CHARACTERISTICS (TA = 0 ~ 70C)

Symbol

Parameter

Test Conditions

V+

I+

PO

AV

BW

THD

PSRR

RIN

IB

Operating Supply

Voltage

Quiescent Current

Output Power

Voltage Gain

Bandwidth

Total Harmonic

Distortion

Power Supply Rejection

Ratio

Input Resistance

Input Bias Current

V+ = 6 V, VIN = 0

V+= 6V, RL =8, THD=10%

V+= 9V, RL =8, THD=10%

V+= 6V, f=1kHz

10F from Pin 1 and 8

V+= 6V, Pins 1 and 8 Open

V+= 6V, RL =8, POUT=125mW,

f=1kHz,

Pins 1 and 8 Open

V+= 6V, f=1kHz, CBYPASS=10F,

Pins 1 and 8 Open

V+= 6V, Pins 2 and 3 Open

Guaranteed Limits Unit

Min Typ Max

4

12

V

8

mA

220 325

mW

480 1000

22

26

30

dB

42 46 50

250

KHz

1.5

%

45

dB

20

150 K

250 600 nA

APPLICATION INFORMATION

GAIN CONTROL

To make the IL386 a more versatile amplifier, two

pins (1 and 8) are provided for gain control. With

pins 1 and 8 open the 1.35 K resistor sets the

gain at 20 (26 dB). If a capacitor is put from pin 1

to 8, bypassing the 1.35 K 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 feeback path. This is done with a series RC

from pin 1 to 5 (paralleling the internal 15 K

resistor). For 6 dB effective bass boots: R15 K,

the lowest value for good stable operation is

R=10 K if pin 8 is open. If pins 1 and 8 are

bypassed then R as low as 2 K can be used.

This restriction is because the amplifier is only

compensated for closed-loop gains greater the 9.

INPUT BIASING

The schematic shows that both inputs are biased

to ground with a 50 K resistor. The base current

of the input transistors is about 250 nA, so the

inputs are at at out 12.5 mV when left open. If the

dc source resistance oriving the IL386 is higher

than 250 K 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 K, 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 unesed input to

ground, equal in value to the dc source resistance.

Of course all affset problems are eliminated if the

input is capacitively coupled.

When using the IL386 with higher gains (by

pessing the 1.35 K 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 F capacitor or

a short to ground depending on the dc source

resistance on the driven input.

2012, February, Ver. 03

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