Yes, the input signal needs to be centered within the input common mode voltage range. This could mean that an opamp operating on +10 V and GND has a max output voltage of only 4 or 5 Vp-p. These can reduce signal voltage range by 6 V peak-to-peak or more. Also, be sure the check the datasheet for the input common mode voltage range and output voltage range. Some opamps require a minimum voltage between the two power pins of 10 V (+10 V, -10 V, +/-5 V, whatever), so single supply operation is possible, but not at 6 V. Yes, almost any opamp can operate with a single power supply voltage but some are way better at it than others. So if R3 were a more reasonable 10K ( and connected to ground through a 1 uF cap), then varing R4 from 10K to 20K would change Q from one to infinity ( at which point the filter becomes an oscillator.) Also keep in mind that changing the Q this way also changes the amplitude. I think only Qs of more than one will be useful here. The best way to do this is to keep R1 equal to R2( roughly) and vary them together to change the center frequency of the filter. Making the resistors independently varible creates a huge range of issues that are too big to cover here. Then when you change the gain ( and Q), by varing R4, the output remains centered around 5.5V.
#Need key for filter forge 5 series
In this application one can make the source oscillate around the 5.5V point, so all that this circuit needs to be single supply compatible is a capacitor in series with R3. 5 and 10.5 volts, so 5.5V would be best which is not that much different than 6V.
Although one usually sees single supply circuits biased at one half V+, the ideal point is actually midway between the output swing of the amps. For a more complete explanation you need to redraw the circuit with component designations.Ĭontinuing my answer using the new schematic.