amplifier instability

is the 4.5mV not the max difference allowed between the positive and negative input? I will be setting the negative input with the pot so it is as close as possible to the positive input. the difference will then be 0-20mV approximately. please let me know if i have misunderstood this

tomas632 said:

is the 4.5mV not the max difference allowed between the positive and negative input? I will be setting the negative input with the pot so it is as close as possible to the positive input. the difference will then be 0-20mV approximately. please let me know if i have misunderstood this

Click to expand...

hi,
If you consider the MCP opa unsuitable I would suggest you do a search for an opa that is designed to work from a single +5V supply and has rail2rail output swing with zero offset/or a nulling feature.

sorry, i think i misunderstood the datasheet. i thought the max input offset voltage was the max differential voltage. i will try an MCP and see if its ok although the OPA241 has the same pin out as my 741 so may try that instead

tomas632 said:

sorry, i think i misunderstood the datasheet. i thought the max input offset voltage was the max differential voltage. i will try an MCP and see if its ok although the OPA241 has the same pin out as my 741 so may try that instead

Click to expand...

hi,
When making experimental PCB's it a good idea to use IC DIL sockets were possible.

Lets know what you find during test.

The input offset voltage is the output error voltage when the DC gain of the opamp is 1. So if the max input offset voltage is 3.5mV, the DC gain of the opamp is 1 and the output DC voltage is supposed to be +2.5V then the output DC voltage will actually be from +2.4965V to +2.5035V. But the voltage divider resistors that set the +2.5V will have much more error.