Hi Addohm,
Your mic preamp and LM386 power amplifier won't work.
The preamp has the input to the TLC072 biased at only 0.089V but the datasheet shows that it must be at least 0.5V. Make it 4.5V.
The mic (dynamic) shorts the input to 0V anyway because there is no input coupling capacitor.
My Electronic Stethoscope was fixed by me, not designed by me so I didn't change its input to be a high input impedance non-inverting type.
Your preamp is a inverting type with a very low input impedance.
The datasheet for the TLC072 explains that it has Cmos inputs that have a fairly high capacitance that causes the opamp to oscillate when its feedback resistor has a high value. It also oscillates when the load capacitance is more than about 100pF. The opamp should have a coupling capacitor feeding the volume control to block DC.
Your LM386 power amplifier is missing the RC network at its output as shown on the datasheet. It will oscillate without them.
Both ICs need a supply bypass capacitor.
Please post your schematic here instead of at ImageShack.
Your mic preamp and LM386 power amplifier won't work.
The preamp has the input to the TLC072 biased at only 0.089V but the datasheet shows that it must be at least 0.5V. Make it 4.5V.
The mic (dynamic) shorts the input to 0V anyway because there is no input coupling capacitor.
My Electronic Stethoscope was fixed by me, not designed by me so I didn't change its input to be a high input impedance non-inverting type.
Your preamp is a inverting type with a very low input impedance.
The datasheet for the TLC072 explains that it has Cmos inputs that have a fairly high capacitance that causes the opamp to oscillate when its feedback resistor has a high value. It also oscillates when the load capacitance is more than about 100pF. The opamp should have a coupling capacitor feeding the volume control to block DC.
Your LM386 power amplifier is missing the RC network at its output as shown on the datasheet. It will oscillate without them.
Both ICs need a supply bypass capacitor.
Please post your schematic here instead of at ImageShack.
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