The isolation amplifier circuit of Figure 1 is simple but accurate. With the values shown it converts 0 to 5V DC or low frequency signals with unity gain, but you can adjust the gain by changing R4.

Here we designed a subwoofer amplifier producing audio signals at low frequencies from 20 Hz to 200Hz and with an output power of 100W, used to drive a 4 ohm load. A Subwoofer is a loudspeaker, which ...