I am trying to design and build a Low Pass Filter ( Active Filter with opamps ) . This will be the front end pre-amplifier as well as filter connected to a coil that will pick up 22hz to 32hz pulses from a Magnetic coil placed 10 feet away . I have used Filter Wiz Lite and Filter LAB2.0 , but both tools suggest using opamp of either TI or Microchip . What i need is a tool or tutorial that help design one using opamp 741 . Any suggestions ???
Basically i need to amplify signal picked up from a Rx coil . The pick up coil has the impedance of 2.4Kohm and its a AWG #44 wire wound air core coil . Actually i do need a pre-amp IC with AGC so that if the TX coil is near or far the gain is controlled . What other opamp or circuit would you suggest , i need a gain x5 or x10 or ideally adjustable
2k4 source impedance .. is in a range wher a bjt or a fet opamp can be used. I'd prefer a low noise bipolar opamp.
Variable gain. You could look for automatic gain control, often made with OTAs, (compressor)
Or you could manually adjust it wit pot. Or control it with microcontroller, e-pot, multiplying DAC, or special opamp with built in gain control.