Wednesday, September 4, 2019

OpAmp audio section

This is the first post I made. I'm revisiting the idea of making an audio amp with an OpAmp. I will use a LM358. It is a dual section amp which doesn't need a dual power supply and will work with a 3 volt supply.

This is the circuit except for the LM308 's in it. I don't have a model for the LM358. The split supply is not needed with the LM358 so The battery goes from top to bottom of the circuit. I made one on a breadboard and it drove a small speaker.
It's not an LM386 but Digikey has them for 30 or 40 cents each. I think I saw them for $15 a hundred. They are dual amps so I used both section set to a gain of 100. It would be a simple matter of changing a feedback resistor to change the gain.

2 comments:

  1. I've got lots of the 358, might just breadboard this.

    Can't have you running sims with wrong parts, here is the TI LM358
    (52 lines as a checksum)

    ** Standard Linear Ics Macromodels, 1993.
    ** CONNECTIONS :
    * 1 INVERTING INPUT
    * 2 NON-INVERTING INPUT
    * 3 OUTPUT
    * 4 POSITIVE POWER SUPPLY
    * 5 NEGATIVE POWER SUPPLY
    .SUBCKT LM358 1 2 3 4 5
    ***************************
    .MODEL MDTH D IS=1E-8 KF=3.104131E-15 CJO=10F
    * INPUT STAGE
    CIP 2 5 1.000000E-12
    CIN 1 5 1.000000E-12
    EIP 10 5 2 5 1
    EIN 16 5 1 5 1
    RIP 10 11 2.600000E+01
    RIN 15 16 2.600000E+01
    RIS 11 15 2.003862E+02
    DIP 11 12 MDTH 400E-12
    DIN 15 14 MDTH 400E-12
    VOFP 12 13 DC 0
    VOFN 13 14 DC 0
    IPOL 13 5 1.000000E-05
    CPS 11 15 3.783376E-09
    DINN 17 13 MDTH 400E-12
    VIN 17 5 0.000000e+00
    DINR 15 18 MDTH 400E-12
    VIP 4 18 2.000000E+00
    FCP 4 5 VOFP 3.400000E+01
    FCN 5 4 VOFN 3.400000E+01
    FIBP 2 5 VOFN 2.000000E-03
    FIBN 5 1 VOFP 2.000000E-03
    * AMPLIFYING STAGE
    FIP 5 19 VOFP 3.600000E+02
    FIN 5 19 VOFN 3.600000E+02
    RG1 19 5 3.652997E+06
    RG2 19 4 3.652997E+06
    CC 19 5 6.000000E-09
    DOPM 19 22 MDTH 400E-12
    DONM 21 19 MDTH 400E-12
    HOPM 22 28 VOUT 7.500000E+03
    VIPM 28 4 1.500000E+02
    HONM 21 27 VOUT 7.500000E+03
    VINM 5 27 1.500000E+02
    EOUT 26 23 19 5 1
    VOUT 23 5 0
    ROUT 26 3 20
    COUT 3 5 1.000000E-12
    DOP 19 25 MDTH 400E-12
    VOP 4 25 2.242230E+00
    DON 24 19 MDTH 400E-12
    VON 24 5 7.922301E-01

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  2. Thank you sir. I'll give it a try.

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