LM388 datasheet(3/8 Pages) NSC

3 / 8 page

Typical Performance Characteristics (Continued)

Swing vs Supply Voltage

Peak-to-Peak Output Voltage

Voltage Gain vs Frequency

Distortion vs Frequency

Distortion vs Output Power

Power4X Load

Device Dissipation vs Output

Output Power8X Load

Device Dissipation vs

Output Power16X Load

Device Dissipation vs

TLH7846 – 6

Application Hints

GAIN CONTROL

To make the LM388 a more versatile amplifier two pins (2

and 6) are provided for gain control With pins 2 and 6 open

the 135 kX resistor sets the gain at 20 (26 dB) If a capaci-

tor is put from pins 2 to 6 bypassing the 135 kX 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 A low frequency pole in the gain response is

caused by the capacitor working against the external resis-

tor in series with the 150X internal resistor If the capacitor

is eliminated and a resistor connects pins 2 to 6 then the

output dc level may shift due to the additional dc gain Gain

control can also be done by capacitively coupling a resistor

(or FET) from pin 6 to ground as in

Figure 7

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 fre-

quency shaping the feedback path This is done with a se-

ries RC from pin 6 to 13 (paralleling the internal 15 kX resis-

tor) For 6 dB effective bass boost R j 15 kX the lowest

value for good stable operation is R e 10 kX if pin 2

LM388 Scheda tecnica(PDF) 3 Page - National Semiconductor (TI)