Hello all,
I have a question for the group...I have built inverting and non-inverting Schmitt Trigger with symmetrical and asymmetrical trigger points using an LM741 op-amp with no problems. I would like to make these same circuits using a single supply op-amp, like the LM324. Is this possible? If so, can I make it asymmetrical so that the lower trigger point is above 0V?
Thanks in advance.
Hi, Zucker. If you've got a single supply, and you want digital output anyway, why not just use a comparator?
The LM393 is a dual single supply comparator that will do the job. Look at the "Inverting Comparator with Hysteresis" application circuit at the bottom of p. 9 of the data sheet for your answer.
The three 1 meg resistors in the circuit allow the switching points at
1/3Vcc and 2/3Vcc. Change the resistors to change the switching points.Good luck Chris
Just replace the 741 with the LM324, and the circuits should work quite similarly, except that the output will swing closer to the negative supply voltage and this will increase the hysteresis, slightly (lower the more negative threshold). There is nothing preventing you from using a
324 in a dual supply circuit.
Yes, there is! An LM324 won't fit into an LM741 socket! ;-)
(IOW, OP will have to rearrangs a few connections. :-) )
Cheers! Rich
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