Help for a circuit schematic explanation

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http://imageshack.us/photo/my-images/685/variablegaincontrol.png/"can someone please explain me the circuit schematic that i have attached because i can't understand it.

Thank youhttp://imageshack.us/photo/my-images/685/variablegaincontrol.png/
 
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  • #2
SteamKing
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I can't understand your circuit because it is not attached to the OP.
 
  • #3
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It looks like either a voltage comparator with a LOT of hysteresis, or an inverting amplifier with gain, where the positive and negative inputs are reversed.

Bob S
 
  • #4
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It looks like a Schmidt Trigger. The output voltage adds to the input and maintains the output at either the + or - rail even with small variations in the input voltage. There is both a positive and negative threshold at which the Schmidt Trigger will change state. They are the input voltages that will cause the voltage at pin 3 of the opamp to cross zero volts. Since R62 is a variable resistor and can be varied between 0 and 10K ohms the threshold voltage can be varied a little. To find the threshold voltage use this formula. (Vcc/(R55 + R62))*R54. For the values given and R62 at 0 ohms, 5K ohms and 10K ohms the thresholds would be 15V, 7.5 V and 6 volts respectively.
 

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