Week Four
Week Four:
25 February 2022
Meeting Attendance:
· Daniel Knight
· Conor Lambe
· Itamar Panzo
Progress during week four:
During this week we fixed the LM386 mono amplifier by adding
a decoupling capacitor to reduce noise from the DC source, and replacing the IC
chip. After this, the circuit amplifies the input as expected, with a gain of
20, but similar to the stereo OPA2134 circuit, the output power is not enough
to drive the 30W speakers. When using a 32Ω set of headphones (which require
less power), however, the audio is amplified as expected with little
distortion.
According to the LM386 datasheet, adding resistors and capacitors
across the pins 1 & 8 can adjust the gain. We added a 10μF capacitor across
these pins, which resulted in a boost of the gain from 20 to 200.
Also, we soldered a copy of the working LM386 circuit onto a
stripboard, with the help of a demonstrator, as this is more similar to what
would be used in an actual amplifier, rather than a breadboard.
LM386 stripboard circuit (wires on right are AC input,
ground, VCC from top to bottom)
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