single-ended BJT MIXER design help!
 

please help me with my design on metal detector.i need to mix my two
sine inputs(few hundreds of KHz)and extract their difference.i opted
for the bjt.my questions a

1.biasing
-- using the buil-in transistor of lm389,how do i bias it such that
it operate in "mixing" mode?

2.diode-based
-- can u share any other simple circuit to implement a mixer in the
low frequency range?


thanks!!!!