PKL
Newbie level 1
New here so if this is not the right location I apologize.
I have a circuit that makes a ramp as shown in the picture. I think the top part of the circuit is being used to supply constant charge to the capacitor C125 in order to get a linear ramp. I think the op amp is acting like a comparator with the reference voltage to compare to being a divider between R121 and R116. From there I get a bit lost. I think R118 is being used to limit the current through the FET to C125 and serves no other purpose? Is R117 required at all? or maybe there is some important interaction between R118 and R117 that takes place? It looks like the output of the opamp will have a varied duty cycle based on the reference voltage at the non inverting input but how this actually works is causing me some grief. Is there any benefit to this configuration over the configuration shown in the application notes? I know it works I just don't fully understand.
TIA,
PK
I have a circuit that makes a ramp as shown in the picture. I think the top part of the circuit is being used to supply constant charge to the capacitor C125 in order to get a linear ramp. I think the op amp is acting like a comparator with the reference voltage to compare to being a divider between R121 and R116. From there I get a bit lost. I think R118 is being used to limit the current through the FET to C125 and serves no other purpose? Is R117 required at all? or maybe there is some important interaction between R118 and R117 that takes place? It looks like the output of the opamp will have a varied duty cycle based on the reference voltage at the non inverting input but how this actually works is causing me some grief. Is there any benefit to this configuration over the configuration shown in the application notes? I know it works I just don't fully understand.
TIA,
PK