re analog switches balanced demodulators msf skaro as arizona edu michael fulbright writes i am trying to build a synchronous demodulator and i ve hit a snag in my application i want to be able to change the gain of an op amp amplifier from to controlable via a digital input the most obvious way i ve come up with is to use analog switches to adjust the gain of the op amp the only analog switch i have experience with it the unfortunately i want to switch an ac signal which goes from about v to v and the is only for positive signals i have recently used the to switch a bipolar signal i simply ran the off a bipolar supply v in this case as long as your analog input signal stays between the supply rails the will work fine of course your control logic input must use v as the logic low and v as the logic high reference so that either all your driving logic must be cmos with the same bipolar supply or you must provide some kind of voltage level shifting circuit between the and the control logic in my case i was able to use the bipolar supply all the way carlos puig kj st cpuig infoserv com san jose ca
