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Questions tagged [multivibrator]

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1answer
63 views

BJT twin transistor astable multivibrator always outputs high

Noob here (again). I have made this schematic of an astable multivibrator and a Raspberry Pi. I want it to produce a square wave, but it just outputs high constantly. I use the Raspberry Pi as a ...
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1answer
58 views

Astable Multivibrator using BC549s not oscillating

I just recently started learning about electrical engineering stuff, and since my final goal of building a Z80 Computer seems a bit far away, for now, I decided I'd make a simple clock I could ...
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3answers
391 views

How to skip the first pulse triggering for this circuit?

Following my previous question, I came up with the following circuit using 74HC123 for simulation and in practice planning to use this IC. The circuit out should be ON when it waits for a rising edge ...
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2answers
79 views

Astable multivibrator malfunctioning on circuit board

Here is the circuit that I've built on my project board (GL-12) Here is a schematic: Note: I'm using BC107B transistors instead of BC547 as they are quite similar. To test the circuit, I added two ...
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1answer
52 views

Using a DSO138 digital oscilloscope to probe a circuit

I'm new to using a DSO138 to probe my circuit. In order to get the square waveform on my DSO for an astable multivibrator, do I need to connect a jumper wire from the collector of a transistor of the ...
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0answers
42 views

Figuring out the importance of components in a circuit-2

This is a follow-up question for this qs which I asked earlier Here is the full specifications- The simulation gives me a current of 6.5 mA through D1 and 833 micro-A through D2. Also, I get the ...
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2answers
55 views

How to actually calculate the rise time for a square wave generated by an Astable Multivibrator?

If I have an astable multivibrator like the one shown in the picture, how do I actually calculate the rise time for the output square wave? I know that it's the time required to change from the low ...
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2answers
56 views

What actually causes the distortion in the output wave due to an Astable Multivibrator?

I've witnessed that the output square wave from an astable multivibrator using two BJTs has its edges rounded during the rise up time(just as it is seen in fig. 1). Across resources, I've come to know ...
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1answer
31 views

Connecting a RC circuit to the output channel of an astable multivibrator (follow up question)

This is a question which I had asked earlier. Tinkering around, I found out that if I connect a capacitor to the load resistor, i.e. if I pass the output through a RC circuit, the voltage retains it ...
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2answers
110 views

Playing around with an astable multivibrator

I had a doubt regarding the astable multivibrators using BJTs. This is a typical astable multivibrator. I have been told that if I connect a capacitor to the output channel, there would be no ...
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1answer
60 views

Astable multivibrator not producing a square output wave, using two BJTs

I've been trying to build an astable multivibrator circuit using two BC547B NPN transistors. I know how to build one using a 555 timer, but I'm having some problems using transistors. I should've ...
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0answers
22 views

Window comparator with transient detection

I need some advice with over range circuitry I my design. In summary, I need to probe two nodes in my circuit and raise an alarm if any of them raises above approx. 2V peak (in both polarities). The ...
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0answers
28 views

PVT indepedent CMOS multi-vibrator design

I am doing a process, voltage, temperature (PVT) analysis of an RC-based multi-vibrator. Simulations under varying temperature (0-100 C) and process corners (FF, FS, SF, SS) show signal delay in the ...
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1answer
77 views

Unstable astable multivibrator

I'm trying to do an ngspice simulation of a 1KHz astable multi-vibrator. While I can achieve oscillations the output is very erratic and all over the place. [edit: two good responses below who said ...
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3answers
247 views

How to read a schematic with capacitors

I've tried many times to read electronic schematics. I always struggle to understand how to read it in order to understand how the circuit works. The most important problem I have is trying to figure ...
1
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1answer
135 views

What is wrong with my circuit and how can I fix it?

This circuit used to work before I soldered it. When I initially soldered it, I used a 6V battery and it was oscillating, but the speaker was very quiet. I went with a 9V battery and I re-soldered ...
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0answers
52 views

How do I eliminate voltage spikes at edges of a pulse?

I am making a Negative edge triggered T flip flop using I2L. Here is a photo of the circuit Its working fine and the output waveform is correct, but there is an undesirable voltage spike at each ...
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1answer
112 views

I don't understand the working principle of this metal detector circuit?

The circuit below is a metal detector circuit. The inductor serves as a "sensor" to detect metal. The tone of the speaker changes when a metal is detected. However, I don't know anything ...
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2answers
155 views

How do I make an edge triggered T flip flop using integrated injection logic (I2L)?

I have been searching everywhere online on how to make this circuit. I found out I can make NAND gates using I2L and connect them together to make a T flip flop , but this is very impractical since I ...
2
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1answer
105 views

Why is the input trigger pulse in a monostable multivibrator fed to the base of the transistors through a capacitor and not an inductor or resistor?

In a monostable multivibrator, one of the transistors will be fed with a trigger pulse using a capacitor. I have heard about capacitor coupled circuits like stagger tuned amplifier where one single ...
4
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2answers
193 views

In an astable multivibrator, why doesn't negative feedback prevent the output from ever saturating?

What I understand of an astable multivibrator so far is this: The output saturates to one of two extremes, which drives the capacitor in the negative feedback loop to either charge or discharge. Once ...
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0answers
52 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
401 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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0answers
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
56 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
71 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 ...
3
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3answers
1k 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
46 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
320 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
48 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?
2
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1answer
71 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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3answers
550 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
94 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
121 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
177 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
56 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
622 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?
1
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1answer
136 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
79 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
26 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
495 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
47 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
93 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 ...
1
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1answer
63 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 ...
0
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2answers
130 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
221 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
79 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
313 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 ...