dl09
Full Member level 4
I feel that some points should be sorted out.
You have been originally asking how to amplify µV signal to mV, with minimal supply voltage.
Later you switched to 1.45 V input voltage and 8V supply. I guess you did so to have a simple problem description. But the solution will be probably different, hence we should agree if we are discussing the first or the latter question. I'm referring to high level amplifier here.
It has been already stated, that the single supply circuit in post #19 only works with an OP that has a input common mode range including the negative supply rail. NJM4558 isn't of this kind. Even with respective OP common mode range (as exposed e.g. by LM358), the inverting single supply amplifier can't amplify a positive input voltage, as also stated.
There are several solutions:
- use dual supply which enables the circuit to amplify signals of positive and negative polarity
- use an OP with input common mode range down to and including the negative supply rail
To amplify a positive input voltage > 1V, NJM4558 can be even used in a non-inverting single supply amplifier configuration. See a simulation circuit with similar RC4558. Please notice that these OPs have no guaranteed common mode voltage range for +/-4V supply, the simulation is based on typical values. The LTspice circuit is also attached.
View attachment 157799
we are discussing the latter question, because i want to make sure i can amplify the signal. so if i use njm4558 in a non-inverting single supply amplifier configuration that will amplify a positive input voltage that is greater than 1 volt?