Hi
My design is an analog audio device.
It has 8 channels, so 16 LM3915s. I do a wide range adjustment of reference voltage and led intesity as described on figure 26, page 17 of the datasheet. I also use the precision half wave rectifier shown on figure 18 page 12 to drive my LM3915s. I am using 2 LM3915s on each channel to drive a very extended range bargraph as described on figure 22, page 14 of the datasheed (Except that the gain of my opamp is 68 instead of 30).
I have added a 100kOhm pull down resistor between my input (10V full scale) and ground to prevent it from floating high. After that I still measure more or less 9mV on my Input. Wich isn't much of a problem for my LM3915 n°2, but after the 36dB amplification, those 9mV are enough to turn on the first led driven by the LM3915 n°1.
My questions are : Is it normal that I measure 9mV on the input of my LM3915 after adding a 100kOhm pull down resistor ? Can I bring that resistor down to 30 or 10kOhms to prevent the first led from my "low levels bargraph" for turning on when OV or no signal is connected to the input ? If so, how do you suggest that I should adapt my Half Wave Rectifier circuit. If I shouldn't do that, what solution do you suggest ?
Thank you very much for your help to a newbie.
