Questions tagged [multivibrator]

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49 views

Very high current frequency on transistor collector

simulate this circuit – Schematic created using CircuitLab I am designing astable multivibrator for homework and I have calculated values for resistors and capacitors (hopefully right) but I ...
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2answers
320 views

Astable multivibrator using op amps - why does it start?

I'm new to electronics and I'm learning some circuits with op amps. Now I have been shown this astable multivibrator. I understand how it works. The op amp is saturated at one side or the other ...
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9 views

Why am I getting a lesser negative threshold voltage for my astable multivibrator?

I've calculated my threshold voltages to be +/-5V but when I probe Vout, I'm getting a -6.42V threshold voltage instead of the expected -5. Why is this? I'm guessing it has something to do with R4 and ...
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1answer
51 views

Current direction in a multivibrator

I have been studying multivibrators lately, but I have hit a wall right now. I have attached a sketch for an astable multivibrator. I know the basic stuff. When Vout is high then Vin will rise as CT1 ...
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1answer
63 views

Analysis of a multivibrator circuit

I have trouble understanding the operation of the following circuit: This is the given description of the schematic: "This is a voltage controlled multivibrator that is used as an acoustic volt ...
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3answers
892 views

How to build an arbitrary (one-shot) pulse generator?

I need a circuit/IC that can generate a single pulse with a variable pulse width (I would want a minimum of 50 ns but if that is not possible the next minimum can be 1 μs, and even if that is not ...
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1answer
44 views

What would be the main advantages of constructing an astable multivibrator with two CMOS inverters?

What would be the main advantages of constructing an astable multivibrator with two CMOS inverters? Can these semiconductor devices be declared to introduce small parasitic capacitances to the circuit?...
3
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1answer
291 views

Astable multivibrator: what starts the first cycle

I think I understand how the astable multivibrator works once the LEDs are blinking (cf. below), but I don't understand how the first cycle begins. I can see that at first, the 2 LEDs are on (based ...
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1answer
47 views

Does the Ebers-Moll BJT model support multivibrators?

I'm developing a circuit simulator and tried to create an ideal astable multivibrator (I set some values not to be completely symmetric for the correct startup). The simulation usually stuck in ...
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0answers
81 views

How can I produce continuous signal from short one?

Can somebody explain, please. How can I produce continuous signal from short one?
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1answer
68 views

Which ground plane shape is more appropriate in my application?

I've been working on re-making the two PCBs in the HP 211A square-wave generator from 1955, as the traces on the one I own are starting to peel off. Focusing on one board, the multivibrator, for the ...
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15 views

A light dependent current astable multivibrator

i have basic knowledge about multivibrators and how a photodiode is operated but i'm having trouble trying to combine them into one circuit. Suppose if i am to operate the photodiode on the circuit as ...
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3answers
281 views

Is this D Flip Flop positive edge triggered or negative edge triggered?

It is an edge triggered D flip flop where X is input, Y is clock, Q is output. Is this D Flip Flop positive edge triggered or negative edge triggered? ADD (copied from a comment): Actually I am trying ...
2
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1answer
92 views

I'd like to know whether my attempt to increase duty cycle will work

I've been looking for a solution to make an astable multivibrator give me a 90% duty cycle or a duty cycle above 50%. This is what I came up with. I have very limited resources and means of testing, ...
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2answers
93 views

Convert Astable Multivibrator square output waveform to sawtooth

I designed an astable multivibrator by using BJT(necessary) to produce a square waveform, my question is how I convert the output signal from a square to a ramp waveform. Thank you
3
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1answer
172 views

What is this circuit called?

This is a circuit I made to create a high signal when a switch is opened and closed. The duration of the signal can be adjusted by changing the capacitors and resistors. It is also low powered when ...
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0answers
37 views

Simulation problem for a multivibrator IC in Proteus

I have the following circuit in Proteus, and I try to simulate the functionality of the 74HC423 multivibrator IC: The problem is whenever I change the values for Rx or Cx, the output's pulse width ...
2
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2answers
573 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
127 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
75 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
23 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 ...
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1answer
341 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 ...
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1answer
46 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 ...
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2answers
89 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
55 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
94 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
188 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
70 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 ...
2
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2answers
252 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
716 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
190 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
143 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
111 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
174 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
675 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
86 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 ...
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1answer
138 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 ...
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6answers
473 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
47 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
75 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
1k 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 ...
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5answers
7k 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
291 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
51 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
127 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 ...
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1answer
879 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
118 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
71 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
74 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 ...