Posts Tagged ‘Filter’

15V Reducing Voltage Regulator Noise

The following circuit is designed for filtering 15 volt supplies like those typically found in instrumentation. The shunt will greatly reduce white noise, spurious signals, and line-related signals on the power supply; the attenuation can exceed 40 dB with careful construction. The values are not critical except that the gain of the amplifier should be very near the ratio of the transistor emitter resistor to the series shunt resistor. In this case the gain is 15/0.05 = 300. Actually the gain is 301 with the indicated values so a 299k resistor would be theoretically better but the resistor tolerances and the actual resistance in the 0.05 ohm shunt path will cause more variation. One of the gain resistors may be made variable to allow the performance to be tweaked for the deepest null, if desired. Choose a low noise metal foil or wirewound potentiometer for best results. Standard fixed values will give excellent noise reduction sufficient for most applications. The LM833 is an excellent choice but many other low noise op-amps will work well. Choose an op-amp with a high bandwidth and low input noise voltage. A higher value shunt resistor may be used if the voltage drop can be tolerated; adjust the gain of the amplifier to match as described above. The LM833 is a dual op-amp so two shunts may be implemented with the one package for filtering two different supplies or for cascading two shunts for additional line rejection and noise reduction. The noise shunt provides no load rejection beyond the rejection provided by the source regulator through the 0.05 ohm resistor.

Read More Source: http://www.techlib.com/electronics/finesse.html
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Low Pass Active Filter by LM741

Low Pass Active Filter by LM741
When you want to filter low frequency gives can change only. I thinks the Low Pass Active Filter circuit help you. Because of it uses IC LM741,then usable easy follow circuit image. We can fix the frequency is cut off get, by equipment value R1=R2 = R , and C1=C2=C When fix give 50Hz frequencies low only that can change. Values Show be valuable about 0dB = 50Hz , -3dB = 250Hz , -50dB = 10kHz Then will see tall frequency 50Hz more cut give until less is finished. This circuit should use dual power supply positive,negative,GND +/- 5V to 18V in order to get a signal that is appropriate most.

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