Hello, I'm trying to make a schmitt trigger with a sinusoidal input , and I want digital type outputs (5V, 0V). Every example I've found assumes Vsat+ and Vsat- are symettric about the X axis.
2007-10-28 05:05:44 · 3 answers · asked by rrossorr 3 in Science & Mathematics ➔ Engineering
by symmetric about the X axis, I mean +Vsat = -(-Vsat)
the values are the same..but one has a negative sign on it
2007-10-28 05:34:24 · update #1
Around the x axis? By x-axis you mean midway between logic levels 0 and 1? Not sure what you're saying here, but..
If you are only interested in the AC component of the signal, AC couple it via a cap to the input of an inverter. The input circuitry of the inverter will DC bias your signal near the switching level. Run the output of the inverter directly into the input of another inverter. Add a 1Mohm resistor from the output of the second inverter (which is your digital output) to the input of the first inverter. This will give you some positive feedback, thus making a Schmidt trigger. Select the cap for the input such that it has no more than 1kohm reactance to the frequency of the input. Adjust the value of the 1Mohm resistor if necessary for proper response. Note that there will be a slight delay (phase shift) in the digital output relative to the input.
BW,
GH
[REPOST] I should add that normally you use a comparator for this app, but the above will generally work fine, unless you need an absolute minimum of phase shift.
2007-10-28 05:21:40 · answer #1 · answered by Gary H 6 · 0⤊ 0⤋
Use a Schmitt trigger IC like CMOS 4093. If the input is sinusoidal, rectify it with bridge diode. Use any peak input voltage from 5V to 15V. The input peak voltage should not exceed the power supply voltage. You will have an output with an amplitude almost equal to the supply voltage. Switching will occur when the input voltage reaches nearly 40% of the supply voltage.
2007-10-28 06:35:21 · answer #2 · answered by eematters 4 · 1⤊ 1⤋
Easiest way is to capacitively couple the signal into your circuit. Put a 100K resistor after the coupling cap for DC restoration and couple the top of it through another 100K or so into the input of a 74C14 (or 'HC14, or VHC14, or 'AC14) and clamp the inputs to Vcc and ground thru a couple of 1N4148's.
Doug
2007-10-28 05:38:24 · answer #3 · answered by doug_donaghue 7 · 1⤊ 0⤋
You could try just putting a simple oscillator on it.
2007-10-28 05:14:48 · answer #4 · answered by styx 45 2 · 0⤊ 0⤋