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.

OpAmp Integrator/LowPass Filter

Status
Not open for further replies.

drkidd22

Member
Hello,

I'm working on a amplifier for a photo detector rated at 0.17A/W. I'm trying to figure out with a circuit that was used before on similar amplifier. I would like to understand what's the purpose of the Diode (D2). I think I got it clear that this is a LPF/Integrator but don't understand why the diode is there. Any references to app notes or ideas will be appreciated.
LPFAmp.PNG
 

Attachments

  • OpAmp_LPF.asc
    2 KB · Views: 138
D2 will allow the output to go above "IS" voltage, but the output will not go below the IS voltage.
 
There is something wrong with using 200 Ohms for R1. If the thing is supposed to be a charge amplifier (integrator), R1 should be much, much higher, like 1 to 10meg?
 
D2 will cause an asymmetric slope to the rising and falling edges of the opamp output in response to an input pulse at the inverting input of the opamp.
 
Besides acting like a clipper, it might be that the diode in the feedback is to make the response logarithmic. It all depends on the polarity of the photo detector and the expected output voltage.
 
The opamp cannot produce enough output current to drive the very low value for R1 anyway.
The time constant for the 100 ohms for R2 and the 100 puffs capacitor is so small that maybe there is no such small amount of time (10 femto-seconds?).
 
Sorry guys, I should've mentioned that the value of R2 shown there is just me playing around with different resistances. And yes, the value of R2 will be much greater than 200ohm.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top