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Help me about comparator
- Thread starter roboticvn
- Start date
I have read but the datasheet doesn't mention. I get this schematic in a video on youtube. Can you help me?
I think that R6 and R7 form the voltage divider. Vjunction=R7/(R6+R7)*Vcc. When V+>V-, Vout jump up to positive saturation approximate Vcc. When V+<V-, Vout from positive saturation to zero. However, i don't understand effect of Vjuntion. I know that a simplest comparator is only a op-amp. It can work without any resistors.
Hello,
Have a look at the following thread:
DC Offset Issue
There is a VERY similar schematic where I introduced the mentioned resistors.
Bertus
Have a look at the following thread:
DC Offset Issue
There is a VERY similar schematic where I introduced the mentioned resistors.
Bertus
As far as I can tell the resistors form voltage dividers. The purpose of the voltage divider is to provide dc offset for the signals coming out of the TL chips. I notice capacitors between TL chips and LM311, I am guessing those are dc blocking capacitors. So the signals are coming out of TL chips, their dc offsets are removed by the dc blocking capacitors. You want to input those signals to LM311, but you also want to shift them because your LM311 only has one power supply. If you don't shift them up, the part of the signals below 0 volts will be blocked (lost in other words). So the voltage dividers provide the dc offset to the incoming signals, now the incoming signals have room to oscillate between 0 and 9 volts. It looks like voltage dividers divide the 9 volts into two halves. So the incoming signals will oscillate around the 4.5 volts.
Lets say for example that you have incoming signal that is 2 volt peak to peak. It oscillates around 0 volts, from -1 to +1 volts (+1-(-1)=+1+1=2 volts peak to peak). If you feed it straight to LM311 with rails at 0 volts and 9 volts, the part of the signal with voltages from 0 to 1 volt will show, the part of the signal from -1 to 0 volts will be lost because your lowest limit is 0 volts (your lowest rail), there is no room for anything smaller like -1 volts. So you introduce the dc offset of 4.5 volts by means of voltage divider. Now your incoming signal has been shifted up, it oscillates around 4.5 volts, from 3.5 to 5.5 volts (5.5-3.5=2 volts peak to peak).
Lets say for example that you have incoming signal that is 2 volt peak to peak. It oscillates around 0 volts, from -1 to +1 volts (+1-(-1)=+1+1=2 volts peak to peak). If you feed it straight to LM311 with rails at 0 volts and 9 volts, the part of the signal with voltages from 0 to 1 volt will show, the part of the signal from -1 to 0 volts will be lost because your lowest limit is 0 volts (your lowest rail), there is no room for anything smaller like -1 volts. So you introduce the dc offset of 4.5 volts by means of voltage divider. Now your incoming signal has been shifted up, it oscillates around 4.5 volts, from 3.5 to 5.5 volts (5.5-3.5=2 volts peak to peak).
The reason I wanted to view the youtube video was to see whatever was presented. As it's written on the schematic, the audio will exceed the reference and not produce the proper full scale PWM. I would call this "over-modulated" but I see that the word "over-modulated" is not in the lexicon of digital schemes.
This is video https://www.youtube.com/watch?v=CCAkpJ-jG6A. Thanks for everyone's help. Thank you very much ^^
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Sorry, I reposted the image. I saw the image but I didn't know what software that is. I just know proteus and circuit maker. Can you show me?Thank you
