Balanced Modulator
    These are from some notes of mine.  I am not exactly sure if this is like the balanced modulator I built, but it is very close.  It should be noted that only one of the CA3280's has the diode bias current.  This is because only one set of diodes is needed to linearize both CA3280's.  This also means that both halves must be in the same package.  This modulator works pretty good, but not as good as a true 4 quadrant multiplier.