Hi There,
I've got a ~3hz waveform coming out of an op amp (0 - 1.8V). I need to turn on an oscillator (~440hz) when the output of the waveform goes high (say anything above 1.0V).
The problem I'm having is that when I hook the output of the opamp to the VDD of my oscillator circuit things don't work. I tried driving the oscillator current via a BJT (running a 10K resistor between the opamp output and the base) but as soon as I connect the output of the opamp to the 10K/base of the transistor I get a square wave on the output of the opamp that's unrelated to my incoming signal (square wave is ~ 1hz or below).
So any advice on how to drive my osciallator circuit? Should I setup an opamp as a comparator and drive the BJT via that comparator?
Power is a concern since I have 400uA at 1.8V to work with.
Here are the two schematics (sorry for any irregularities, this is a work in progress). I had trouble with the IMG tag so here are some url's.
http://images5b.snapfish.com/232323232fp63284>nu=3549>897>257>WSNRCG=3279;;<5;;348nu0mrj
http://images5b.snapfish.com/232323232fp63263>nu=3549>897>257>WSNRCG=3279;;5874348nu0mrj
Thanks!
I've got a ~3hz waveform coming out of an op amp (0 - 1.8V). I need to turn on an oscillator (~440hz) when the output of the waveform goes high (say anything above 1.0V).
The problem I'm having is that when I hook the output of the opamp to the VDD of my oscillator circuit things don't work. I tried driving the oscillator current via a BJT (running a 10K resistor between the opamp output and the base) but as soon as I connect the output of the opamp to the 10K/base of the transistor I get a square wave on the output of the opamp that's unrelated to my incoming signal (square wave is ~ 1hz or below).
So any advice on how to drive my osciallator circuit? Should I setup an opamp as a comparator and drive the BJT via that comparator?
Power is a concern since I have 400uA at 1.8V to work with.
Here are the two schematics (sorry for any irregularities, this is a work in progress). I had trouble with the IMG tag so here are some url's.
http://images5b.snapfish.com/232323232fp63284>nu=3549>897>257>WSNRCG=3279;;<5;;348nu0mrj
http://images5b.snapfish.com/232323232fp63263>nu=3549>897>257>WSNRCG=3279;;5874348nu0mrj
Thanks!
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