Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [schmitt-trigger]

Anything related to Schmitt trigger circuits. Schmitt triggers are positive feedback comparator circuits exhibiting hysteresis.

Anything related to Schmitt trigger circuits. Schmitt triggers are positive feedback comparator circuits exhibiting hysteresis, i.e. the input threshold for which the comparator output changes state depends on whether the input signal is increasing or decreasing. This mechanism allows for greater noise immunity.

See also Wikipedia on Schmitt triggers.

254 questions
10
votes
3 answers

What is a Schmitt Trigger and its application exactly?

i would like to ask about what is a Schmitt Trigger and about its application. I searched a lot but still didn't understand it. Please explain step by step and hope you help me in its applications in real circuits.
user3213767
  • 455
  • 2
  • 6
  • 11
9
votes
1 answer

Does the 74LVC1GU04 actually have "Schmitt-trigger action" on its input?

The 74LVC1GU04 is an unbuffered inverter, which (according to the datasheet) is intended to be used in linear mode in applications, such as crystal oscillators and linear amplifiers with negative feedback. But the same datasheet claims that there is…
johnfound
  • 5,307
  • 1
  • 16
  • 31
9
votes
4 answers

How do I make an opamp comparator work in schmitt-trigger mode?

I want to control a small 12V case fan. I will set values of R1, R2 and R3 so that the fan will work above temperatures 40oC. I understand that in these kind of systems, there will be an indecisive region in which the comparator output will be fast…
hkBattousai
  • 13,913
  • 31
  • 114
  • 190
9
votes
1 answer

Disadvantages of Schmitt Trigger Inputs

I'm familiar with the utilization of Schmitt Triggers when interfacing with low slew rate signals / sinusoidal waveforms. In a recent design, I've been scrubbing our FPGA I/O configurations and noticed that I left the Schmitt Trigger on for a lot of…
Krunal Desai
  • 6,246
  • 1
  • 21
  • 32
8
votes
1 answer

How does a "speed up capacitor" work in Schmitt trigger?

Hello I'm trying to understand how adding a capacitor across R2 in below circuit increases the switching speed. I don't see how C2 supplies charge to C1. With the additional capacitor C2, it seems the output voltage has to charge one additional…
AgentS
  • 591
  • 6
  • 18
8
votes
2 answers

Can multiple Schmitt triggers in series fully debounce a switch?

After dealing with software debouncing for a while, I find it takes a huge toll on the system, so I thought of initially making a hardware debouncer with one Schmitt trigger (74HC14), a capacitor, button and resistor as shown below from…
Mike -- No longer here
  • 755
  • 5
  • 20
8
votes
5 answers

Hardware debouncing of key matrix with minimum passive components

I have recently bought this cheap 4x4 keypad matrix. It only has the push-buttons and nothing else therefore I want to add a proper debouncing to it. The debouncing in software is something I want to avoid because it takes some processing power out…
DEKKER
  • 755
  • 1
  • 12
  • 23
8
votes
3 answers

Using CMOS Schmitt trigger inverters in quartz crystal oscillator circuit

In all sources I've seen about quartz crystal oscillators using CMOS inverters there's a note like this: But why Schmitt inverter is needed? Won't classic 74HC04 work?
bokjezd
  • 105
  • 1
  • 1
  • 5
8
votes
2 answers

In a 74HC14 Schmitt trigger IC, unused inputs/outpus

I have a 74HC14 Schmitt trigger IC. I only use one of its I/O pairs, and everything else is not used. I understand that in TTL logic the unused inputs should be set to either high or low to prevent floating pins. But I wonder, can I set the outputs…
futureshocked
  • 183
  • 1
  • 4
7
votes
6 answers

Is a Schmitt-trigger output’s rise time affected by input pulse’s rise time?

I know that a Schmitt-trigger makes rising edge of an input pulse sharper. But is the rise time of the output pulse affected by the input’s rise time? How can this be shown by simulation or shown mathematically with an example?
GNZ
  • 1,559
  • 4
  • 25
  • 52
7
votes
4 answers

Why is this derivation of Schmitt trigger circuit's output signal, incorrect?

This is the reference Schmitt trigger circuit. Using KVL, \$V_x\$ turns out to be \$\frac{R_1}{R_1+R_2}V_o\$. Also, $$V_o = A\left( V_x - V_i\right)$$ $$V_o = A\left( \frac{R_1}{R_1+R_2}V_o - V_i\right)$$ $$\left( \frac{R_1}{R_1+R_2} - {1\over…
Akash Karnatak
  • 295
  • 3
  • 7
6
votes
2 answers

Switching on an SSR on positive voltage and turn it off on negative voltage

I am currently trying to "hack" my way through a door lock, whose PCB cannot be changed. The task is to replace the motor for turning the cylinder with a Solid State Relay. However, the only contacts available are the ones of the motor itself. Some…
Sofia Braun
  • 83
  • 5
6
votes
2 answers

Comparator with hysteresis equations

I'm trying to be sure I'm computing the values for this circuit right. Here's an example of the circuit I'm trying to build (it's going in a 12 V DC system, so I filled that in already). I have a textbook from electronics class several years ago…
Matthew
  • 289
  • 2
  • 3
  • 8
6
votes
6 answers

Discrete Schmitt Trigger: make output logic level at 0V, not 3V

I designed a Schmitt Trigger with discrete components (using an emitter-coupled pair) that operates with a Low Disable Trigger of around 3.5V and a High Enable Trigger of around 4V on circuit simulation. The circuit simulation uses a sine wave…
Pan Ziyue
  • 161
  • 1
  • 2
5
votes
1 answer

Working of Hex Schmitt−Trigger Inverter as a Sawtooth and Square Wave Producer

Can someone explain how a Schmitt Inverter can behave as a Sawtooth (on pin 1) and a Square wave (on pin 2) as produced in a circuit where we have a Capacitor between pin 1 and GND, and a resistor between pin 1 & 2.
Sherby
  • 2,316
  • 6
  • 27
  • 44
1
2 3
…
16 17