Need circuit for microvolt detection

[numair_noor]

Hi,
I am looking for a circuit to measure the voltage of a DNA dipole. The voltage could be around 125 micro volts. but it could be better to have a circuit which could detect between 50uV to 200uV.
looking for earliest replies.
thank you.

 

[asdf44]

Is it an AC or DC signal?

You'll want to pay particular attention to input offset voltage and offset current of the front end amplifier you chose. You'll want input offset voltage hopefully << your measurement range and as importantly, low drift on both parameters (worst case you can run a cal processes right before your measurement to zero out any offsets, low drift makes this possible).

You'll find that chopper stabilized amps and their variants often have these parameters.

But you should provide more info about the source. What leakage currents are acceptable?

 

[D.A.(Tony)Stewart]

A DNA Dipole is a charge voltage and as such the load impedance must be extremely high on the amplifier so as not to discharge the dipole as well as low capacitance relative to the sensor electrodes and medium.

A suitable choice would be any good low noise JFET Preamplifier design.

https://www.linear.com/product/LT1793 is one.

 

[asdf44]

Offset voltage of the LT1793 is larger than the signal being measured and the drift is up to 50uV/C. The input current is good, but the offset voltage isn't close to good enough for this.

 

[D.A.(Tony)Stewart]

Yes of course, sorry, I was too quick....take 2

Any chopper-stabilized integrated "Zero"drift" JFET OpAmp will do.