Hi Guys,
I'm jumping in with my first post on this forum, because I have an issue with the LM3915 wich is very similar to lowprofile's. The difference is that I am using a very extended range bargraph except that the gain of my opamp is 39 dB instead of 30dB.
I had the same problem, of input of my LM3915 n°2 floating high. I used a 100k pull down resistor between LM3915 n°2's input and groud wich solved the problem even though I still measure more or less 9mV on that input when it's not loaded. But, after the 39 dB opamp, those 9mV become enough to turn on the first led driven by the LM3915 n°1.
My LM3915's are driven by the Precision Half Wave Rectifier circuit suggested in the datasheet. (attached)
My questions is : Is it normal that I still measure 9mV on the input of my LM3915 n°2 after adding a 100kOhm pull down resistor ?
Should I be bringing that pull down resistor value down to 30 or 10kOhms to prevent the first led from my "low levels bargraph" from turning on when OV or no signal is connected to the input, or should I also use a 100k pull down resistor on the input of LM3915 n°1.
Thank you very much for your help to a newbie.
I'm jumping in with my first post on this forum, because I have an issue with the LM3915 wich is very similar to lowprofile's. The difference is that I am using a very extended range bargraph except that the gain of my opamp is 39 dB instead of 30dB.
I had the same problem, of input of my LM3915 n°2 floating high. I used a 100k pull down resistor between LM3915 n°2's input and groud wich solved the problem even though I still measure more or less 9mV on that input when it's not loaded. But, after the 39 dB opamp, those 9mV become enough to turn on the first led driven by the LM3915 n°1.
My LM3915's are driven by the Precision Half Wave Rectifier circuit suggested in the datasheet. (attached)
My questions is : Is it normal that I still measure 9mV on the input of my LM3915 n°2 after adding a 100kOhm pull down resistor ?
Should I be bringing that pull down resistor value down to 30 or 10kOhms to prevent the first led from my "low levels bargraph" from turning on when OV or no signal is connected to the input, or should I also use a 100k pull down resistor on the input of LM3915 n°1.
Thank you very much for your help to a newbie.
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