i need to build a diff op amp for two different setups (see attached schematics).
Q1 is driven by a PWM signal
R8 is the load
R7 is 0.1ohm
i know the basics for diff amp gain as:
when R3=R4 and R2=R5
Vout = R2/R3*(V2-V1) where V2 is on +in and V1 is on -in of amp.
my question is if these two op amp circuits will function exactly the same way? i question the setup that has V1 tied to ground.
do i really need R4 and R5 (i dont really need to divide the +in voltage), just do a simple divided neative feedback like this one here http://www.allaboutcircuits.com/vol_3/chpt_8/5.html. perhaps the +in divider is needed if the voltage there +Vin is too high for the +in, etc.
also, in the 1st pic the load is inductive and Q1 will be protected by a 33v zener. so i guess i need to be careful choosing a amp and perhaps need R4 and R5 to knock that voltage down to the amp...?
do i have this right?
Q1 is driven by a PWM signal
R8 is the load
R7 is 0.1ohm
i know the basics for diff amp gain as:
when R3=R4 and R2=R5
Vout = R2/R3*(V2-V1) where V2 is on +in and V1 is on -in of amp.
my question is if these two op amp circuits will function exactly the same way? i question the setup that has V1 tied to ground.
do i really need R4 and R5 (i dont really need to divide the +in voltage), just do a simple divided neative feedback like this one here http://www.allaboutcircuits.com/vol_3/chpt_8/5.html. perhaps the +in divider is needed if the voltage there +Vin is too high for the +in, etc.
also, in the 1st pic the load is inductive and Q1 will be protected by a 33v zener. so i guess i need to be careful choosing a amp and perhaps need R4 and R5 to knock that voltage down to the amp...?
do i have this right?
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