Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

op-amp problem

Status
Not open for further replies.

tarik321

New Member
Hi Everyone,
I have an ac current source of the order of 30 nA pp, whenever I use a resistor 500k to convert the current to voltage I get an output signal ( ac voltage ) but when I used a current to voltage converter using an op-amp 741cn and a resistor 500k I don’t get any signal, can u help me figure out this dilemma ?

thanks a lot

Tarik
 
Hi Everyone,
I have an ac current source of the order of 30 nA pp, whenever I use a resistor 500k to convert the current to voltage I get an output signal ( ac voltage ) but when I used a current to voltage converter using an op-amp 741cn and a resistor 500k I don’t get any signal, can u help me figure out this dilemma ?

thanks a lot

Tarik

hi,:)
Whats the frequency of the 30nAppk signal.?

Can you post your 741 circuit drawing.
 
30nA?

It sounds like you need a FET imput opamp, I doubt the lame old 741 will be good enough.
 
Hi,

this is the circuit with 741CN OP-AMP

thanks

Tarik
 

Attachments

  • photo.GIF
    photo.GIF
    9.6 KB · Views: 1,234
What is the signal source? What is the opamp output? Where is your input resistor?
 
The input bias current of a lousy old 741 opamp is typically 80nA but is a max of 500nA at room temperature. Look at its datasheet.

The input bias current of a Fet-input TL071 opamp is typically only 65pA but is a max of 200pA at room temperature, it is low noise and its frequency response is much better so it has more internal gain at any frequency.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top