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.

rectifying a differentiator

Status
Not open for further replies.

Dr_Doggy

Well-Known Member
so the differentiator works but now i am trying to rectify the output so the transistor will switch on not only during a positive pulse but also on a negative pulse, i assume the easiest way to do this is to use a rectifier, but don't know how to ground it, any suggestions?? maybe there is a easier way to it?? maybe use Zener diodes??

If it helps LED1 is going to be replaced with power sourcing to an op amp pot configuration much like the outer circuit
 

Attachments

  • op3.png
    op3.png
    7.4 KB · Views: 242
You don't ground the rectifier, you connect it in series with the output you are rectifying, with a capacitor at the diode output to ground to store/smooth the rectified value. You may also need a resistor in parallel with the cap to discharge the cap before the next pulse.
 
i can do the resistor and capacitor but could we draw that rectifier on pls?

my instincts tell me that both should go to my ground since the transistor I'm powering goes to ground but that just doesn't seem right
 
Your instincts are a little off. Just put the rectifier in series between the source and resistor/capacitor. You do know what series means, don't you?
 
If you're looking for something to do an absolute value, you can try the attachment. It works because the Texas Instruments OPAx374 Op-Amp series clamps its output to ground when it would otherwise try to go negative

Before you try it, there's a few things you should know.
  • First, the op-amp needs to be able to handle negative inputs without damage or phase reversal. LM324 may not be compatible. TI's OPA2374 is recommended.
  • Second, it works best if the input has no DC offset, so you might want to add another 10uF capacitor in series with R1.
  • OpA2374 runs on 5 Volts normally. You may need a voltage divider at your LM324 output. (details later)
  • If R2=R3, the overall transfer function is Vout = |Vin|
  • R1 limits the input pin current. The OPA2374 can withstand momentary negative inputs as long as R1 is large enough. I'd go with 10k to 100k.

It may seem like a lot of trouble compared to other methods, but this is one low-distortion option.

[1] Smith, Anthony H., "Full-Wave Active Rectifier," Electronic Design, vol. 57, num. 16, p51, Aug 2009
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top