0
\$\begingroup\$

I've put together an lm386 audio amplifier circuit as shown in the image below. The volume was good when hooked up to the 9V output on my trainers breadboard, but when I hooked it up to a 9V battery, I couldn't get any sound out of it. I measured an 8V voltage drop when between the positive and negative end of the circuit on the breadboard and a 2V voltage drop with the same circuit powered by a 9V battery.

This makes me wonder where all the power is going (if not through the audio amplifier) in the battery-connected circuit. I am guessing that there is greater current from the breadboard, which pushes electrons through the circuit, but would like a more definitive answer. credit: AfroTechMods

credit AfroTechMods

\$\endgroup\$
  • 1
    \$\begingroup\$ current does not push electrons, voltage pushes electrons .... the movement of electrons is current \$\endgroup\$ – jsotola Dec 15 '17 at 8:30
  • \$\begingroup\$ bad 9V battery or bad breadboard? \$\endgroup\$ – jsotola Dec 15 '17 at 8:31
  • 1
    \$\begingroup\$ I imagine the 9 V battery can't supply the current the load wants so the output voltage falls. \$\endgroup\$ – TonyM Dec 15 '17 at 8:56
  • \$\begingroup\$ You used to be able to buy a small speaker box with a built in LM386 amplifier. Those boxes had a single 9V battery for power. They worked well enough. So, this ought to work. It doesn't, though, so you've done something wrong. \$\endgroup\$ – JRE Dec 15 '17 at 9:24
  • \$\begingroup\$ I'll dig up a datasheet later and see where your circuit is different from the suggested circuit. \$\endgroup\$ – JRE Dec 15 '17 at 9:25
1
\$\begingroup\$

ESR of all batteries is inverse to mA rating so 9V battery is more than the DCR of a speaker.

I trust you understand how impedance divider reduces voltage.

What ESR did you expect?

There is a wide tolerance on this inverse relationship but is always true for the technology or chemistry.

\$\endgroup\$
0
\$\begingroup\$

turned out to be the battery. My multimeter was reading 9 volts, but when I swapped the Walgreens battery for a Duracell, it fixed all my problems :)

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.