MisterBill2
- Joined Jan 23, 2018
- 18,176
Possible.The falling edge of the scope waveform seems to show about 5 oscillations in the space of ~0.2uS, so a frequency of ~25MHz?
Possible.The falling edge of the scope waveform seems to show about 5 oscillations in the space of ~0.2uS, so a frequency of ~25MHz?
In my Lm 393 comparator, my output is not coming proper square wave.picture is shown below.i have described about my circuit. practically
I am using voltage comparator LM393 for comparing two signals, one signal is my reference signal which is a triangle wave, with voltages 2.08 volt generated by 555 timers above 200kHZ giving to the input terminal of inverting side of LM393 and input signal or modulating signal which voltage is less than 2.08 giving from function generator as a sinusoidal signal in the range of 1 Hz to 20kHz in the noninverting side of LM393. My question is when I am providing two signals it should be compared and give a square wave, but LM393 only taking triangle wave, sin wave is not going? why I don't understand. please give suggestion to the above points. In this picture below, I am referring to this circuit, please tell me what 's wrong in this circuit, when I am taking triangle wave from 555 timer ad providing into the comparator and another signal providing from the generator. View attachment 210902View attachment 210903
I understand your point. let I explain you everything before you want to conclude anything .i am generating triangle wave from TLC 555 timer, I have also attached pictures shown below, in the real-time practical performed, I have seen triangle wave coming, it looks like a sawtooth wave but it's okay .carrier frequency is above 200 kHz, the output voltage is 2.14 vpp . if you carefully my triangle wave is coming with dc offset(look at arrow ground ref in the scope), now I am giving this signal to the lm393 inverting port, now I am providing audio signal conserving all input common voltage range .it should be less than 2.14 volt, audio frequency 1 Hz to 20 kHz. now when I am providing to the 3rd pin or non-inverting pin in lm393, the output signal is coming in the above picture. I will upload one more picture. , my question is how I can improve square wave, and one more thing still I have connected this lm393 output with hex inverter, I am only connected with 10 k pull up resistor. only . Help me.R6 pull-up is too high a value to drive the stray capacitance at that frequency, giving the rounded rise-time.
Reduce its value to about 1.3kΩ.
Note: Never leave CMOS inputs floating as you show for U3.
Connect all unused inputs to ground.
In my Lm 393 comparator, my output is not coming proper square wave.picture is shown below.i have described about my circuit. practically
I am using voltage comparator LM393 for comparing two signals, one signal is my reference signal which is a triangle wave, with voltages 2.08 volt generated by 555 timers above 200kHZ giving to the input terminal of inverting side of LM393 and input signal or modulating signal which voltage is less than 2.08 giving from function generator as a sinusoidal signal in the range of 1 Hz to 20kHz in the noninverting side of LM393. My question is when I am providing two signals it should be compared and give a square wave, but LM393 only taking triangle wave, sin wave is not going? why I don't understand. please give suggestion to the above points. In this picture below, I am referring to this circuit, please tell me what 's wrong in this circuit, when I am taking triangle wave from 555 timer ad providing into the comparator and another signal providing from the generator. View attachment 210902View attachment 210903
Both posts#2and #3 stated that the pull-up resistor for the comparator output is much to high a value. That alone will explain the long rise time and why it is not a nice rectangular wave-shape. And I see the photo of the assembly and no bypass capacitor across the power terminals of the comparator. And still no hysteresis in the comparator and quite long leads on most of the circuit.I understand your point. let I explain you everything before you want to conclude anything .i am generating triangle wave from TLC 555 timer, I have also attached pictures shown below, in the real-time practical performed, I have seen triangle wave coming, it looks like a sawtooth wave but it's okay .carrier frequency is above 200 kHz, the output voltage is 2.14 vpp . if you carefully my triangle wave is coming with dc offset(look at arrow ground ref in the scope), now I am giving this signal to the lm393 inverting port, now I am providing audio signal conserving all input common voltage range .it should be less than 2.14 volt, audio frequency 1 Hz to 20 kHz. now when I am providing to the 3rd pin or non-inverting pin in lm393, the output signal is coming in the above picture. I will upload one more picture. , my question is how I can improve square wave, and one more thing still I have connected this lm393 output with hex inverter, I am only connected with 10 k pull up resistor. only . Help me.
okay, I got your point. so I will do 3 three things,1- reducing the value of pull up resistor,2- adding a bypass capacitor into the power lines,3-add a 1M resistor connecting with pin 2 and pin 1 (inverting and output ) this point refers the hysteresis .please correct me where I am wrong . and I am going to upload my new results asap. I would like to add, I am not connected to the output of the comparator with hex inverter or any circuit. the circuit only consists of TLC 555, Lm393 only.Both posts#2and #3 stated that the pull-up resistor for the comparator output is much to high a value. That alone will explain the long rise time and why it is not a nice rectangular wave-shape. And I see the photo of the assembly and no bypass capacitor across the power terminals of the comparator. And still no hysteresis in the comparator and quite long leads on most of the circuit.
Jn addition, comparator switching is better with higher drive levels,
The feedback resistor goes to the NON-INVERTING input, so that should be correct.okay, I got your point. so I will do 3 three things,1- reducing the value of pull up resistor,2- adding a bypass capacitor into the power lines,3-add a 1M resistor connecting with pin 2 and pin 1 (inverting and output ) this point refers the hysteresis .please correct me where I am wrong . and I am going to upload my new results asap.
Thanks, can you tell me what would be the value of the bypass capacitor 0.1uf?The feedback resistor goes to the NON-INVERTING input, so that should be correct.
I am heading out to work now so my response will be later.
I am not connected my Lm393 comparator output hex inverter till yet. I am only measuring my output from lm393comparator only.Did you connect all of the 74HC04 unused inputs to ground like crutschow told you to?
still, I do not solder hex inverter on my board till yet.I am not connected my Lm393 comparator output hex inverter till yet. I am only measuring my output from lm393comparator only.
should I remove the breadboard wires ?Your messy long wires on the breadboard are causing the LM393 comparator to oscillate at a high frequency, each time its output goes low.
Why do you use a huge potentiometer with long wires instead of using a trimpot with short leads?
Why are the parts on the breadboard so far apart?
should I remove the breadboard wires ?
if you are here please give some valuable comments on circuit and present results .pleaseThe feedback resistor goes to the NON-INVERTING input, so that should be correct.
I am heading out to work now so my response will be later.
okay, sir, I will follow your comment and will remove potentiometer and put a trim pot. any other comments you want to say, in a way to improve my circuit.Audioguru is right, at those frequencies component placement and trace paths on a PCB becomes very important. I suggest you take a look at this post if you want to learn how to make a proper PCB. The expensive paper cited in that post is no longer necessary, as I discovered that the backing paper of adhesive vinyl film can be also used. With the proper technique of course.