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.

LM324 opamp output variations

earckens

Member
A pcb made according to the schematic (attached below) uses LM324 opamps. With no input signal to the current transformer pin 3 should be low, and pin 2 follows feedback from output pin 1 (high).
Two of the opamps give 0.0V on their pin 1, but two opamps measure approx. 2.5V on their outputs.

All components are correctly soldered with correct values on the pcb, hence I would expect five identical results.

Pcb traces to pins 2 and 3 are just millimeters long, and as short as possible.

Jumpers SJx are not soldered.

I swapped IC's around, but still the same circuits of the five do show this behaviour, hence unrelated to the IC's.

Why are two outputs not near 0V?
 

Attachments

  • current detector model RR v10.pdf
    48.3 KB · Views: 14
Last edited:
Voltage on all input pins may tell you why the output is low or high. 1st stage has a gain of +101..
Maybe some diodes are reversed D1 etc
 
Voltage on all input pins will tell you why the output is low or high.
Maybe some diodes are reversed D1 etc
No, diodes all are of correct type and orientation.

The opamp stage in question has a x1000 amplification, so the output has to be either low (0V) or high (Vcc - 1 or 2V).

So for an output being 'low' then 2V is pretty high, isn't it?
 

Latest threads

New Articles From Microcontroller Tips

Back
Top