Electronics > Projects, Designs, and Technical Stuff
Generating Biphasic Signal with OpAamp
schmitt trigger:
--- Quote from: A.Ersoz on August 28, 2019, 01:48:57 pm ---I have one more question. How can I make biphasic signal as sharp rising and falling edge? In my signal which is attached, there is a little ramp 0 to positive and positive to negative changing?
--- End quote ---
Slew rate limitation perhaps? Please post the opamp's data sheet.
And with your scope, measure the slope of the little ramp.
Lastly, Increase both the vertical sensitivity and the horizontal timebase, such that the ramp may be measured accurately.
A.Ersoz:
The Opamp is TLV27L1 and its datasheet is attached.
StillTrying:
--- Quote from: A.Ersoz on August 28, 2019, 01:38:15 pm ---
--- Quote from: StillTrying on August 27, 2019, 02:14:05 pm ---The bottom op amp needs a DC path from its +ve input to 0V.
--- End quote ---
Can you describe a little more your comment
--- End quote ---
At DC the cap C2 330nF is open circuit, and so is the op amps +ve input because of it's very high input impedance, so the voltage there just floats about, sometimes it might be floating near 0V other times it will float towards the +5 or -5V rails.
A 1M resistor between the op amos +ve input and 0V would do to keep the floating voltage close to 0V.
With 2 inputs, 2 op amps, 2 outputs, and only using 1 scope channel at a time it's impossible to work out what your trying to do. :)
A.Ersoz:
Actually, the opamp at the bottom is connecting with a mux. So it is not floating.
What do you think about the ramp of the signal in the previous post?
schmitt trigger:
Page 4 of the datasheet, indicates an unity gain slew rate (at 25C) of 0.06 V/usec typical. Could be a little better, could be a little worse. Nevertheless, this is one slow opamp.
Also you have a cap in parallel with the feedback resistor, which would also further limit the slew rate (and no, I have not made the corner frequency calculations).
Your image indicates that the slew rate is approximately 0.052 V/usec.
Thus, I believe you are indeed hitting opamp slew rate limitations. You require to find a faster opamp. Use the selector data sheets from the supplier's web pages.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version