Questions tagged [multivibrator]

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2answers
461 views

Bypass capacitor in 555ic

What will happen if we don't bypass capacitor at pin 5 of 555 ic as an astable multivibrator.Will voltage/current changes in line affect on pulse width?will capacitor at pin 1 discharge late?
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1answer
113 views

What's the purpose of the capacitor in this circuit?

If this trigger pulse is starting the process of sweep generation, seems to me like it would be going directly to the base of the transistor (Q701) to switch it on and off, so the series of multiple ...
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1answer
69 views

Some confusions on a basic CMOS multivibrator question

This is a previous exam question, so I do have a solution already, I am not trying to make you solve my homework etc. Few questions in my mind regarding this question above, There is not a given ...
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1answer
22 views

Switching circuit based on clock

I have attached the timing diagram. I want something similar to monostable multivibrator but with so additional features. don't know how the circuit will be. Case 1: I want the output to go high at ...
0
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1answer
53 views

Op-amp astable multivibrator with single supply

I want to create a simple circuit to flash a LED with one op-amp. I already simulated the circuit (astable multivibrator) but there is one problem with the supply. I don't know what to change so that ...
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4answers
7k views

How does this astable multivibrator circuit with FETs work?

I am having trouble understanding this schematic. I do understand that it is pretty simple, but I just can't seem to get my head around part of it. The schematic is a more complicated version of an ...
0
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1answer
45 views

How to find the exact value of K for SN54LS123

I have a circuit containing SN54LS123 (Datasheet) IC. I want to know the output pulse width but unable to figure out the value of K. The formula is PW = K * R * C. The values of K is given in the ...
2
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2answers
69 views

Polyphase multivibrator (real vs SPICE simulation)

i have a following schematic for three-phase multivibrator: SPICE simulation shows that it should work (11 volts peaks on collector nodes): However, when i make this circuit on breadboard it does ...
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1answer
39 views

Timed one-shot circuit to drive laser module

I'm trying to adapt my Match Guns MGH1 (Air pistol with electronic trigger) to use trigger a laser when shooting. Currently the trigger circuit is driving a solenoid. The circuit board seems to have ...
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2answers
60 views

Astable Multivibrator Doesn't Vibrate

I'm trying to get this variation on the classic circuit to work. Pardon the awkward VCC label. The voltage is 4.5 volts, though these batteries are only supplying 4 at the moment. I have an LED and a ...
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2answers
133 views

Replacing an NE555 with a 74HC123D

I want to replace an NE555 with a 74HC123D in a battery powered device. It is used to clock a CD4017, for which I need a pulsed signal of 46Hz. I read that a 74HC123D needs less power than a 555. How ...
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2answers
51 views

Can we trigger a mono-stable multi-vibrator( using 555 IC ) using mono audio signal?

I'm working on a project where, a certain low frequency audio spike should trigger the mono-stable multi-vibrator. If we can trigger a mono-stable multi-vibrator using a mono audio signal, how much is ...
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1answer
113 views

Simple low power rising and falling edge enabled circuit

I am working on a project where I use an esp8266 and a reed switch sensor (NO), this is powered by a battery so I need a low power circuit that can turn on the esp8266 when the state of the reed ...
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2answers
301 views

Op-Amp variable pulse generator

I'm having trouble designing a circuit using an Op-Amp (741) to generate pulses. The task given to me is: Design a pulse generator with a duty cycle that is adjustable from 0 to 100% and whose ...
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2answers
116 views

Why does adding this low pass-filter to a monostable multivibrator prevent triggering?

A 24 VDC sinking sensor is tied to an SSR. The SSR converts the signal from 24 VDC to 5 VDC. The output of the SSR goes directly to input B of a 74121 One-shot. (The diagram has a resistor and ...
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1answer
79 views

Two questions about astable multivibrators and transformers

Here's something that confuses me: The output on an astable multivibrator will be shown on a multimeter as half the input voltage (for example we have 9V-0V-9V-0V...and the multimeter averages it out ...
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2answers
104 views

Is this the proper way to create a high voltage (low current) straight DC signal from a 9V battery?

My goal is to create a circuit that will take in a 9V DC battery as input and produce a high steady +1500V DC signal. I don't need high current at all. 1 microamp of current will do. The scheme goes ...
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2answers
111 views

Astable multivibrator not working

I was wondering if you can help me to know why my circuit is not working. I have tried with different pre-existing circuit values to make sure the circuit was working properly before I put my ...
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1answer
339 views

Fundamental CMOS astable multivibrator

So i need to perform analysis of simple astable multivibrator circuit shown in the following picture: These Vdd and GND are just the power rails of those CMOS inverters. Now, i need to perform ...
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0answers
69 views

Astable multivibrator inverter

I'm new to electronics and trying to make an astable multivibrator oscillator. The PSpice simulation doesn't work (it says netlist error when I place a mosfet or a diode) and I get a really low ...
0
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1answer
80 views

Pulse width stretching of the 0 pulse with a constant T [closed]

I have a digital output with varying pulse sizes and I want to design an IC to stretch the 0 output for a constant T+ "0" pulse time (as in attached picture). I have tried using a monostable ...
0
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6answers
282 views

Pulse width limiter Circuit

I have a mosfet controlling power to a heater. I send pulses (akin to pwm) to tell the mosfet to turn on and send current to the heater. The pulses are coming from a Beagle Bone Black. The process on ...
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2answers
45 views

Explain how this astable chain(?) circuit works

The circuit below fades on and off a cascading series of leds in an alternating fashion. I tried reproducing it on a breadboard with 5 leds to try to understand it how it works, and got all sorts of ...
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1answer
65 views

Op-Amp Astable Multivibrator - Effect of bypass Switch

For your consideration, I have this Astable-multivibrator via a classic Op-Amp Schmitt Trigger delivering a square signal (here 1.82Hz). I am fine with the circuit with SW1 open as C2 is basically in ...
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3answers
719 views

Adding Diodes to Transistor Astable Multivibrator; 1N5818 Schottky diodes work but 1N4148 diodes don't; can't figure out why

I am an avid electronics hobbyist, not an electronics engineer. I built a transistor-based astable multivibrator circuit and then fed its output to an op amp buffer amplifier which then drove an 8 ...
50
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5answers
6k views

Why does music synthesizer built from chain of astable multivibrator circuits get “out-of-tune” after a few hours?

I built a prototype keyboard/sound synthesizer using a chain of 13 astable multivibrator circuits whose outputs are connected to an audio amplifier chip (LM386) and speaker, all powered off a 9V DC ...
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2answers
149 views

BJT Astable Multivibrator - What is the max. oscillation frequency?

What is the max. oscillation frequency of this Astable Multivibrator circuit? Is it directly related to transition frequency of the transistor? I plan on using it with BC547B transistor. The hardwired ...
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0answers
50 views

Upgraded flipflop square wave generator - did I do good?

I've drawn up a simple multi-frequency square wave generator, based on a astable multivibrator circut, with frequency trimmed by the two ganged pots (both 100k) and the range set by a DPDT switch, ...
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1answer
114 views

IC 555 as monostable multivibrator

How is the output of a monostable multivibrator affected if the trigger pin is kept at a negative voltage (0V)? The upper voltage reference comparator will change its output to logic 1, while the ...
0
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1answer
445 views

What is the purpose of higher-resistance resistors in Astable Multivibrator circuit?

The astable multivibrator circuit has two higher-resistance resistors (47k on the pic). What are they there for? Wouldn't it work without? And what is exactly their function? I spent a lot of time ...
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2answers
99 views

Philicorda phase shifter vibrato circuit doesnt work

I have built this circuit in the online editor, but it doesn't seem to oscillate. My philicorda vibrato broke down and i want to repair it. It should convert 21V DC into a sine wave when i understand ...
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0answers
56 views

Astable multivibrator

I found an Astable multivibrator schematic online and the transistor they used was a NPN 2n2222 and I didn't have one so I was just wondering if it's a must to use a specific NPN or PNP for ...
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1answer
64 views

monostable Eccles - Jordan multivibrator, theory

I’ve a few problems and questions to the principle of monostable multivibrator’s work. Basic schematic is as below: What is the reason for D1, C1, R3 elements at input? Why I can’t just tie a ...
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0answers
68 views

Circuits that take advantage of tolerances in components

Bit of a wordy question title... I was trying to simulate an astable multivibrator the other night and the simulation refused to run. I eventually realised that because the simulation assumes perfect ...
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2answers
90 views

Analog Bistable Memory

I am looking for a device which I do not know exists. I would like to store the state of a number of analog switches, perhaps driven by a D Type Flip Flop. I'd like to drive the flip flop and set ...
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2answers
41 views

Should analogue multivibrator and comparator pullup circuit have separate supplies?

I have managed to produce a design within the falstad circuit simulator for an analogue "LED chaser" using an analogue multivibrator and 3 comparators inspecting the voltage of one side of the ...
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1answer
319 views

Astable 555 not oscillating [closed]

I've been struggling with building a 555 timer for a project. I get the expected voltage at pin 3 (output), but the problem is that it's not oscillating. The Vout is constantly 8.4V, while I expected ...
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3answers
286 views

CMOS frequency of oscillation

How to find the frequency of oscillations in this circuit CMOS circuit: simulate this circuit – Schematic created using CircuitLab Assuming the ideal CMOS gate with the threshold at 0.5Vdd. ...
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1answer
59 views

A question about circuit design with a multivibrator

I want to implement a pulse extender with a retriggerable multivibrator IC called CD74HC123EE4. Here is the datasheet. The input will be a 32Hz pulse train with a 5 µsec duty cycle; and at the output ...
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1answer
242 views

Monostable multivibrator problem

As you see in the picture above, diode voltage drop is 0V, and the monostable multivibrator is made in CMOS technology with protection diodes. I have problem finding the output of this circuit in some ...
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0answers
376 views

A monostable multivibrator using two NPN transistors works as desired in LTSpice, but in reality is very different

I designed a simple monostable multivibrator to extend a pulse of width \$\approx\$ \$1{\mu}s\$, to \$8ms\$ (to illuminate an LED when something happens on a bus). This is the circuit here, and the ...
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2answers
361 views

nand gate astable vibrator do not work at 400kHz

I want to build a 400kHz square wave oscillator with NAND GATE using the CD4011BE circuit. Unfortunately, it does not work as expected when I use R2 and C values according this schematic: ...
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2answers
2k views

Astable multivibrator using transistor

I have started learning transistors few weeks ago and I hit a roadblock (again). I have been following this tutorial on Sparkfun -https://learn.sparkfun.com/tutorials/transistors Now I have moved to ...
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2answers
342 views

Controlling which transistor turns on first in a multivibrator

I've managed to adapt a basic multivibrator circuit to contain 3 LEDs that blink in sequence, but I want to be able to control which LED lights first when it's turned on, so the same LED lights first ...
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2answers
238 views

Naive VCXO design - runs at 3rd harmonic, I need the base freq

Consider this a hobby question. (How do you call a hobby project on the fringe of your nominal work? A skunkworks job?) I mean to say that I'm not an EE design pro. I'd appreciate your opinion about ...
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2answers
1k views

Bistable Multivibrator using discrete transistors

I am trying to understand this circuit but as of yet I still have a number of gaps in my reasoning. So far I have deduced: (assuming TR1 is ON and TR2 is OFF) left hand side capacitor charges ...
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3answers
1k views

How to determine the saturation level when an opamp schmitt trigger starts worknig?

The Opamp inverting schmitt trigger is constructed as shown. The output signal is So I ask why is the output at the start of operation saturated to positive? Also, if the input voltage is moved ...
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2answers
952 views

Replacing push button by transistor in 555 circuit

TL;DR: I need to replace the button S1 by a circuit/component that could close the circuit which the button is closing by applying a 5V signal (with 0.5s duration) in the new circuit/component. Well, ...
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1answer
633 views

Opamp Astable Multivibrator - initial delay

I'm trying to build a low frequency oscillator (think about 0.01Hz - 5Hz) using a TL072 as an astable multivibrator. Here's the circuit in LTspice: And here's the simulated output: Where does the 2....
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1answer
530 views

Is this an astable multivibrator?

In this circuit the LED flashes on and off, however could it be classified as an astable multivibrator?