awan
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I'm not sure, what you mean with this statement. Obviously, a single supply AC amplifier or filter needs in- and output levels biased by some amount to provide bipolar voltage swing without saturation. A bias to mid-supply is a common solution, depending on the circuit topology, also a virtual ground at 1.5V may be suitable.I cant push the input to 1.5volts
awan said:I need to design 250Hz sallen key filter and looking for good opamp. I only have single supply at 3volts. I used AD824 and my design works for +3volts and -3volts supply. But it doesnt work for +3volts and 0 supply although the data sheet says that its a single supply opamp.
Yes, it's seems so.But the filter simulation doesnt work; so i am thinking that I am missing some important concept in it.
awan said:Its a Low Pass filter for 0-250Hz. I understand the dual-supply operation; but need help in converting it into a single supply.
E-design said:Use the multiple feedback sallen key topology for better performance. Make sure the op amp you select will have good low output impedance in the required stop band to avoid re-entry. Pick your RC values with low C and high R combinations. This will reduce feed through effects.
awan said:I understand the unity gain LPF with single supply voltage but is it possible to get gain rather than unity gain.
In case i need to get gain with single supply; then the resistance R3,R4 controlling the gain would be connected to virtual ground(0.5Vcc) rather than the actual ground. Am I correct in this? Or we cant have gain from S-K LPF with single supply voltage.
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