Hi! I've only soldered a few circuits before. Tomorrow I am planning on building a mono audio amplifier with a LM386 IC. I've a thread about it here (including a link to the schematic I am working from) https://forum.allaboutcircuits.com/threads/166673
The schematic uses a 9V battery, but I'd rather use a "wallwart" power adapter instead. This is fairly new territory for me - I've mostly just been using 9V batteries so far.
Based on the research I've done, my plan is to connect a 12V AC to DC power adapter to my circuit with a 2.1mm DC barrel jack and then to a L7809 Voltage Regulator.
My understanding is that you need to use a higher value adapter than regulator, because the regulator needs a couple of volts to turn on (read: a 9V regulator won't work with a 9V adapter).
Positive connection from the barrel jack goes to the Input pin of my L7809 Voltage Regulator.
Ground pin of the L7809 to ground connection of the barrel jack (I'll probably go through an on/off switch first).
L7809 Output pin should then have a nice regulated 9 Volts to supply the LM386 and other components of my circuit.
Most sources I studied recommend a 0.33uf capacitor between the L7809 Input and Ground pins and a 0.1uf capacitor between the Output and Ground pins to "smooth out ripples". That seems straight forward enough.
Now, the Amplifier schematic also calls for some decoupling capacitors near the power source, specifically a 100uf and a 0.1uf to filter out low and high frequency noise from the power supply.
Should I put the noise filtering capacitors before or after the voltage regulator?
My intuition tells me it probably won't matter much, except it might give the capacitors a bit longer life if I put them after the voltage regulator since they'll only be getting hit with 9V instead of unregulated 12V. But perhaps there are other considerations I'm not aware of...
Also, if I already have a 0.1uf capacitor between the Ground and Output pins of the L7809 to filter out the ripple, does that make the 0.1uf capacitor of the high frequency noise filter redundant?
Finally, a more general L7809 question - these legs are very long. Is it safe to clip off the excess after it's been soldered in place?
Thanks for reading! Any answers or relevant feedback/tips are most welcome.
Edit: corrected capacitor value from 0.033uf to 0.33uf
The schematic uses a 9V battery, but I'd rather use a "wallwart" power adapter instead. This is fairly new territory for me - I've mostly just been using 9V batteries so far.
Based on the research I've done, my plan is to connect a 12V AC to DC power adapter to my circuit with a 2.1mm DC barrel jack and then to a L7809 Voltage Regulator.
My understanding is that you need to use a higher value adapter than regulator, because the regulator needs a couple of volts to turn on (read: a 9V regulator won't work with a 9V adapter).
Positive connection from the barrel jack goes to the Input pin of my L7809 Voltage Regulator.
Ground pin of the L7809 to ground connection of the barrel jack (I'll probably go through an on/off switch first).
L7809 Output pin should then have a nice regulated 9 Volts to supply the LM386 and other components of my circuit.
Most sources I studied recommend a 0.33uf capacitor between the L7809 Input and Ground pins and a 0.1uf capacitor between the Output and Ground pins to "smooth out ripples". That seems straight forward enough.
Now, the Amplifier schematic also calls for some decoupling capacitors near the power source, specifically a 100uf and a 0.1uf to filter out low and high frequency noise from the power supply.
Should I put the noise filtering capacitors before or after the voltage regulator?
My intuition tells me it probably won't matter much, except it might give the capacitors a bit longer life if I put them after the voltage regulator since they'll only be getting hit with 9V instead of unregulated 12V. But perhaps there are other considerations I'm not aware of...
Also, if I already have a 0.1uf capacitor between the Ground and Output pins of the L7809 to filter out the ripple, does that make the 0.1uf capacitor of the high frequency noise filter redundant?
Finally, a more general L7809 question - these legs are very long. Is it safe to clip off the excess after it's been soldered in place?
Thanks for reading! Any answers or relevant feedback/tips are most welcome.
Edit: corrected capacitor value from 0.033uf to 0.33uf
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