Design of non-inverting schmitt trigger circuit

[Pradeepbp]

Hi,
I want to design a non-inverting schmitt trigger circuit with VTL= -8V, VTH=0V and VOH=5V, VOL=0V.
checked in net, the formula given is VTH = R1/R2 * Vsat. But I need VTH to be zero. And im quite confused with the design concept here.
Can somebody pour some light? Please explain your approach.

 

[Electro nS]

what if R2>>>R1 example : R2=100k , R1=100ohm or 1k . the Vth will be very small , which comparable to zero does this work with your needs??

another way is to use a comparator with an opamp that operate with 0 and 5v supply like : LM368

 

[FvM]

The good guys give a schematic or a link along with theirs post...

 

[BradtheRad]

This simple trick with a potentiometer can be used to add a few volts to your incoming signal, while attenuating it, so that it occupies the positive polarity.



Or, you can use an op amp in summing configuration to achieve the same thing, although you need to provide it with a bipolar supply.

Your schmitt trigger stage is next.

Or with some ingenuity it might be possible to do all jobs with a single op amp.

 

[Pradeepbp]

Hi, Thanks for your reply.
Previous stage of opamp is a summer circuit. So i can shift voltages. Now I have configured my summer circuit to output voltage between 0 to 10V.
I need a non-inverting schmitt trigger circuit with Vl=(0 or 1V) and Vh = (10 or 9V). (I can provide 1 V tradeoff for noise and attenuation).

My problem is designing the schmitt trigger circuit.
VOH/ +Vsat can be 15V or 10V or 5V. VOL/-Vsat has to be 0V. Schmitt ckt drives a switching circuit of next stage.
I checked 741, if i ground -Ve power terminal, then i can get a voltage swing of +Vsat to 13V and -Vsat to 0V.
Now how to design the circuit?

Here is the graph what i need:

Im trying to design with this figure..


But not getting. Should i give any Vref?
Do explain your result. Or send any link where i can study 'design for any given Vl and Vh.
Thanks

 

[FvM]

- Connect a voltage divider (R3/R4) from supply to the inverting OP input to provide an adjustable reference voltage
- Derive expressions for low and high threshold voltages
- Calculate R1/R2 and R3/R4 ratio to meet your specifications

Rather visually, R1/R2 ratio sets the hysteresis (difference between both threshold voltages) and R3/R4 jointly shifts both thresholds

 

[erikl]

Good guys give a schematic or a link along with theirs post...

SCNR. Nix fuer ungut, Frank! ;-)

 

[erikl]

i can get a voltage swing of +Vsat to 13V and -Vsat to 0V.

You can always down-divide or shift voltages (s. BradtheRad's posting above). For Schmitt-trigger action + shifting the input and output voltage with a single opAmp, try something like this: View attachment Schmitt-Trigger4.sch.pdf