Odysseas
Member
Hello there,
I have built an amplifier, which I want to use to amplify the voltage drop across a current sensing shunt.
Here's the schematic: **broken link removed**
The left part is a simple charge pump, which creates a negative supply voltage for the OP07 in the right part. I have already constructed the curcuit and it works - almost.
The OP07 in the right part is configured as a basic differential amplifier - in theory it should amplify any voltage difference between the two pads marked Shunt High and Shunt Low with a factor of 390. It does, however, only when the voltage on the input is referred to ground.
However, my current sensing resistor is on the high-side, i.e. Shunt High is practically tied to +12V. Now, even when there is no current flowing through the shunt (i.e. no voltage difference between Shunt High and Low), the amplifier outputs close to 12V. But when I disconnect the shunt from +12V and let it float, the OP07 outputs close to 0V.
It would seem that the basic idea behind the circuit is flawed. Can anyone please help me with this?
Thanks!!
I have built an amplifier, which I want to use to amplify the voltage drop across a current sensing shunt.
Here's the schematic: **broken link removed**
The left part is a simple charge pump, which creates a negative supply voltage for the OP07 in the right part. I have already constructed the curcuit and it works - almost.
The OP07 in the right part is configured as a basic differential amplifier - in theory it should amplify any voltage difference between the two pads marked Shunt High and Shunt Low with a factor of 390. It does, however, only when the voltage on the input is referred to ground.
However, my current sensing resistor is on the high-side, i.e. Shunt High is practically tied to +12V. Now, even when there is no current flowing through the shunt (i.e. no voltage difference between Shunt High and Low), the amplifier outputs close to 12V. But when I disconnect the shunt from +12V and let it float, the OP07 outputs close to 0V.
It would seem that the basic idea behind the circuit is flawed. Can anyone please help me with this?
Thanks!!