Hello all!
I am new to op-amps and have a few questions I either haven't looked in the right places or googled the right phrases...
In this circuit R2 is actually a variable resistor with 68 ohms being the highest value I will be concerned with. R1 and R2 are a simple voltage divider to create a decent input. I plugged it into my breadboard to see how close things match up and was happy to find the values are close to what I had expected from my calculations. My meter shows 3.82 volts as Vout. I have not measured my resistors to see if they are at marked values which could be causing a bit of the difference along with whatever the op-amp is skewing things.
Having said that... voltage for Vcc is 5V and 0V for gnd. I am using a lm324... mainly because I have 4 such inputs I want to monitor. My questions are... will Vout ever be more than Vcc? According to my calculations if I put 5 volts to Vin I should have a Vout of 65 volts correct? If Vout cannot be more than Vcc (which I assume is, but wanted a for sure answer) then the resistor/zenner pair on Vout won't be necessary as they were simply a way to limit what my PIC will see on the a/d pin. Would a different op-amp be more closer to ideal or a better choice? Like I said the only reason for this choice was because of the quad op-amp package.
Thanks for looking this over and any suggestions / criticism you may have. I've been researching these for a while without trying anything (for why I have no idea!!) I just seemed to have a tough time getting a grasp on things... then I actually tried!! I am planning on trying different values for R3 and R4 over the weekend... or I may leave them be. I would like to see closer to say 4.75V for Vout with R2 at 68 ohms.
I am new to op-amps and have a few questions I either haven't looked in the right places or googled the right phrases...
In this circuit R2 is actually a variable resistor with 68 ohms being the highest value I will be concerned with. R1 and R2 are a simple voltage divider to create a decent input. I plugged it into my breadboard to see how close things match up and was happy to find the values are close to what I had expected from my calculations. My meter shows 3.82 volts as Vout. I have not measured my resistors to see if they are at marked values which could be causing a bit of the difference along with whatever the op-amp is skewing things.
Having said that... voltage for Vcc is 5V and 0V for gnd. I am using a lm324... mainly because I have 4 such inputs I want to monitor. My questions are... will Vout ever be more than Vcc? According to my calculations if I put 5 volts to Vin I should have a Vout of 65 volts correct? If Vout cannot be more than Vcc (which I assume is, but wanted a for sure answer) then the resistor/zenner pair on Vout won't be necessary as they were simply a way to limit what my PIC will see on the a/d pin. Would a different op-amp be more closer to ideal or a better choice? Like I said the only reason for this choice was because of the quad op-amp package.
Thanks for looking this over and any suggestions / criticism you may have. I've been researching these for a while without trying anything (for why I have no idea!!) I just seemed to have a tough time getting a grasp on things... then I actually tried!! I am planning on trying different values for R3 and R4 over the weekend... or I may leave them be. I would like to see closer to say 4.75V for Vout with R2 at 68 ohms.
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