This design is a two-channel desktop power amplifier based on the LM1875 power amplifier chip.
The project is made public for the first time; the project is original; the project has not won any prize in other competitions; it has not participated in any defense in school.
This design is under the GPL3.0 open source license
The main body of this amplifier is two LM1875 chips. The chip has excellent performance and can reach an output power of 25W under a 8 ohm load of plus or minus 25V power supply, which can be used in a small room. Regarding the circuit, we refer to the circuit in the TI chip manual and set an amplification factor of 21 times. You can also get appropriate output power by directly using a mobile phone as the audio source. The feedback network uses Panasonic's 0.1% precision electrical chip resistors, which can reduce the PCB area and the wiring length of the feedback network to reduce the introduction of noise, and also improve the symmetry of the left and right channels. Four film capacitors are connected to the rectifier bridge of the power supply to eliminate diode noise. The main filter capacitor is a pair of Panasonic 4700UF electrolytic capacitors. The main capacitor is a small film capacitor to filter out high-frequency noise. A decoupling capacitor group is also added near the power supply pin of each chip to provide a good power supply condition for the power amplifier. A protection circuit based on UPC1237 is added to the output end of the power amplifier. Its main function is to eliminate the impact of the power amplifier on the speaker when the power is turned on and to disconnect the connection between the power amplifier and the speaker when the power amplifier outputs a DC voltage fault to achieve the purpose of protecting the speaker.
| ID | Name | Designator | Footprint | Quantity | BOM_Manufacturer Part | BOM_Manufacturer | BOM_Supplier | BOM_Supplier Part |
|---|---|---|---|---|---|---|---|---|
| 1 | 2.2uF | C1,C30 | CAP-TH_BD8.0-P3.50-D0.6-FD | 2 | ||||
| 2 | 47uF | C2,C32 | CAP-TH_BD8.0-P3.50-D0.6-FD | 2 | ||||
| 3 | 0.1uF | C3,C4,C13,C31 | CAP-TH_L7.2-W2.5-P5.00-D0.6 | 4 | ||||
| 4 | 0.22uF | C5,C11 | CAP-TH_L7.2-W6.0-P5.00-D0.5 | 2 | PE224J2A0501 | KYET | LCSC | C393118 |
| 5 | 100uF | C6,C7,C14,C29 | CAP-TH_BD8.0-P3.50-D0.6-FD | 4 | EEUFM1H101 | PANASONIC | LCSC | C128473 |
| 6 | 15pF | C8,C9,C10,C12 | C0805 | 4 | CC0805JRNPO9BN150 | YAGEO | LCSC | C107110 |
| 7 | 4700uF | C15,C16 | CAP-TH_BD18.0-P7.50-D1.2-FD | 2 | ECA1VHG472 | PANASONIC | LCSC | C178403 |
| 8 | 100uF | C17 | CAP-TH_BD6.3-P2.50-D1.0-FD | 1 | ERS1VM101E12OT | AISHI | LCSC | C106694 |
| 9 | 223 | C18 | CAP-TH_L7.2-W2.5-P5.00-D0.6 | 1 | ||||
| 10 | 47uF | C19,C20 | CAP-TH_BD5.0-P2.00-D0.8-FD | 2 | KM470M035C110A | CapXon | LCSC | C74117 |
| 11 | 10uF | C21 | CAP-TH_BD5.0-P2.00-D0.8-FD | 1 | 10uF 25V 5*11 | ValuePro | LCSC | C43347 |
| 12 | 220uF | C22 | CAP-TH_BD8.0-P3.50-D0.6-FD | 1 | ERE1VM221F12OT | AISHI | LCSC | C106510 |
| 13 | 100nF | C27,C28 | CAP-TH_L7.2-W2.5-P5.00-D0.6 | 2 | C242A104J2SC000 | FARATRONIC | LCSC | C280716 |
| 14 | 10nF | C33,C34,C35,C38,C39,C40 | CAP-TH_L7.2-W2.5-P5.00-D1.0 | 6 | ||||
| 15 | GBU8K | D1 | GBU_4P-L22.0-W3.5-P5.08 | 1 | ||||
| 16 | 1N4007_C727081 | D2,D6,D7 | SMA_L4.4-W2.8-LS5.4-RD | 3 | 1N4007G-T | Diodes Incorporated | LCSC | C516593 |
| 17 | G2R-2-DC12V | K1 | RELAY-TH_G2R-2-DCXX | 1 | G2R-2-DC12V | Omron Electronics | LCSC | C48903 |
| 18 | 2A5G3HD01 LED | LED1 | LED-SMD_L5.0-W2.7-FD | 1 | 2A5G3HD01 LED | KENTO | LCSC | C3649 |
| 19 | 1M | R1,R7 | R0805 | 2 | ERA6AEB105V | PANASONIC | LCSC | C445668 |
| 20 | 22K | R2,R10 | R0805 | 2 | ERA6AEB223V | PANASONIC | LCSC | C445659 |
| twenty one | 1K | R3,R15 | R0805 | 2 | 0603WAF1001T5E | UniOh | LCSC | C21190 |
| twenty two | 20K | R4,R6,R8,R9 | R0805 | 4 | ERA6AEB203V | PANASONIC | LCSC | C473304 |
| twenty three | 1R/2W | R5,R18 | RES-TH_BD5.0-L15.5-P19.50-D0.7 | 2 | MFR02SF100KA10 | UniOh | LCSC | C69885 |
| twenty four | 56K | R11,R14,R19 | R0805 | 3 | PTFR0805B56K0N9 | ResistorToday | LCSC | C351560 |
| 25 | 10K | R12 | R0805 | 1 | AC0805DR-0710KL | YAGEO | LCSC | C723677 |
| 26 | 3.9K | R13 | R0805 | 1 | RK73H2ATTD3901F | KOA Speer Elec | LCSC | C317270 |
| 27 | 2K | R16 | R0805 | 1 | RMC08052K5%N | Tyohm | LCSC | C269731 |
| 28 | 10R/2W | R17 | RES-TH_BD4.5-L11.5-P15.50-D0.7 | 1 | - | Chian Chia Elec | LCSC | C119561 |
| 29 | LM1875L-TB5-T | U1,U2 | TO-220-5_L10.5-W15.5-P1.70-TL | 2 | LM1875T/NOPB | TI | LCSC | C9666 |
| 30 | UPC1237 | U3 | SIP-8_L19.2-W2.8-P2.54-L | 1 | ||||
| 31 | 7812 | U4 | TO-220-3_L10.0-W4.5-P2.54-L | 1 | MC7812BTG | ON | LCSC | C45387 |
| 32 | DB128L-5.08-2P | U5,U8,U9,U10 | CONN-TH_2P-P5.08_DB128L-5.08-2P | 4 | DB128L-5.08-2P | DIBO | LCSC | C395868 |
| 33 | DB128L-5.08-3P | U6 | CONN-TH_DB128L-5.08-3P | 1 | DB128L-5.08-3P | DIBO | LCSC | C395869 |
More details: https://diy.szlcsc.com/posts/06c94d90c2c447dfbd9ed7339ff4a5b1
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