Exploring the lm1875 Audio Amplifier Part 2

Some additional exploration and testing of the lm1875. This time, a look at output power by power supply voltage as well as a look at thermal properties.

Testing Results

V power supply (+/-) V in rms V out rms Load (ohms) P out (watts) I (amps) Case Temp (c) Heatsink Temp (c)
5 .095 2.04 8 .52 .255
5 .78 1.8 4 .405 .450
10 .223 5.02 8 3.15 .628 37.5 36.0
10 .182 4.2 4 4.41 .952
12 .285 6.22 8 4.83 .778 43.0 45.5
12 .236 5.4 4 7.29 1.35
15 .360 7.7 8 7.4 .963 56.5 50.3
18 .452 9.75 8 11.88 1.22 67 60.5
20 .508 11.0 8 15.125 1.375 72 71.6
22 .577 12.4 8 19.22 1.55

notes:

Tests executed from laptop headphone jack on battery power using 1khz sine wave
Heatsink AAVID 530002B02500G thermal resistance of 2.5 c/w
Room temp at time of test, 24.2 c
Each temperature test run for 5 minutes before measurement

Resources

Texas Instruments LM1875 datasheet
JohnAudioTech - LM1875 monoblock audio amplifier build
JohnaudioTech - DIY audio amplifier test tone with built in reference