Need equal +,- power supply

Hello friends,


I am working with a instrumentation amplifier to measure current.I am using MC1458 dual op amp.I am giving power supply from 7805 and 7905.outputs from these power supplies are not same (5.2v and -5.4v). so it affects the op amp gain.Is there any way to salve this problem?I have attached my circuit diagram

How much current do you require?
There are a number of ways to balance the outputs.
The simplest is to add a 1k pot to the common line of the 7805 and a 100R in parallel. This line draws about 10mA and by adjusting the pot you can get up to nearly 0.9v increase.

First of all, technically, that's not an instrumentation amplifier. Second, whatever problem you are having with gain is not due to an imbalance in the power supply voltages. If you are operating the circuit at a point where the power suppy imbalance is obvious at the output, the circuit is not operating linearly (it is saturated) where circuit gain is significantly lowered even if there was no imbalance in power supply voltages. Maybe your input level is too high, or there is some other issue. For example, maybe the circuit is supposed to operate saturated and gain is not the real issue.

It looks like you want to come off a current transformer and apply precision rectification and amplification (signal conditioning). I suggest you give this a read as it should help.

Ron

The value for R4 in your circuit is not correct.
The power supply voltages do not affect gain.

rather odd power supply too. i'm not sure the 7805 and 7905 can maintain a virtual ground on their own. you might want to consider using a center tapped transformer or some kind of rail splitter.

unclejed613 said:

rather odd power supply too. i'm not sure the 7805 and 7905 can maintain a virtual ground on their own. you might want to consider using a center tapped transformer or some kind of rail splitter.

Click to expand...

Obviously they can't, I imagine that he's simply left the centre tap off the diagram?.