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LM358 as an audio amp

M

Mike Warren

Jan 1, 1970
0
The LM358 datasheet doesn't specify EIN or S/N. I assume that's
because it's not very good, but using one would simplify my
circuit greatly as I only have +5V available without a lot
of extra work. I need to buffer an audio signal and add a gain
of 2. The input is about 1VRMS.

THD is not super important, but I wouldn't like to add a lot
of noise.

Has anyone used a LM358 in a similar situation successfully?
 
P

Phil Allison

Jan 1, 1970
0
"Mike Warren"
The LM358 datasheet doesn't specify EIN or S/N. I assume that's
because it's not very good, but using one would simplify my
circuit greatly as I only have +5V available without a lot
of extra work. I need to buffer an audio signal and add a gain
of 2. The input is about 1VRMS.

THD is not super important, but I wouldn't like to add a lot
of noise.

Has anyone used a LM358 in a similar situation successfully?


** For non critical applications, within the audio band and with a gain of
only 2 - there is no problem.

However - 2 times 1 volt rms is MORE than 5 volts peak to peak !!

Beware: If the output of the LM358 is cap coupled to the next stage, then
a load resistor to ground is essential to eliminate severe x-over
distortion.

See the Nat Semi 1994 data sheet - page 6.




...... Phil
 
M

Mike Warren

Jan 1, 1970
0
Phil said:
"Mike Warren"


** For non critical applications, within the audio band and with a gain of
only 2 - there is no problem.

However - 2 times 1 volt rms is MORE than 5 volts peak to peak !!

Beware: If the output of the LM358 is cap coupled to the next stage,
then a load resistor to ground is essential to eliminate severe x-over
distortion.

See the Nat Semi 1994 data sheet - page 6.


Thanks, Phil. That's enough for me to build a test circuit.
 
J

Jamie

Jan 1, 1970
0
Mike said:
The LM358 datasheet doesn't specify EIN or S/N. I assume that's
because it's not very good, but using one would simplify my
circuit greatly as I only have +5V available without a lot
of extra work. I need to buffer an audio signal and add a gain
of 2. The input is about 1VRMS.

THD is not super important, but I wouldn't like to add a lot
of noise.

Has anyone used a LM358 in a similar situation successfully?

It looks like it will do what you need.

Have you thought about using a LMV358 ?
THat operates at 2.7..5.5 volts.

THe LPV358 is also lower in current but does
introduce more noise. Which seems to be a big
jump compared to the first 2.
 
J

Jamie

Jan 1, 1970
0
Phil said:
"Mike Warren"




** For non critical applications, within the audio band and with a gain of
only 2 - there is no problem.

However - 2 times 1 volt rms is MORE than 5 volts peak to peak !!

Beware: If the output of the LM358 is cap coupled to the next stage, then
a load resistor to ground is essential to eliminate severe x-over
distortion.

See the Nat Semi 1994 data sheet - page 6.




..... Phil
Page 8 in the Oct 2005 edition.
 
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