Re: Wideband Active filter
The bias problem has been mentioned for the low pass circuit, that needs to be fed by a DC coupled generator to work correctly.
A standard lab generator e.g. would work.
Unfortunately you didn't tell about the observed problems. "Cannot work" is somewhat unspecific, isn't it?
Did you understand the required "feedback resistor" point? When you operate a high frequency current feedback OP without it,
it will oscillate at a x00 MHz frequency with high amplitude, run hot and even may be damaged. High frequency OPs are required
to drive high output currents and are ususally not fully protected.
According to the datasheet, a 500 ohm resistor between output and inv. input would allow stable operation. Making it e.g. 1 kOhm
reduces the loop gain and can improve the circuit stability, if you don't need the full OP gain-bandwidth product.
You should add feedback resistors and then start with DC bias point measurements of the circuit. Just cut the connecting
traces between the two pins and solder a small (e.g. 0603) chip resistor to the pins, for both amplifiers. Alternatively, you can use
a voltage feedback dual OP with compatible pin assignment in the circuit.