Need Help with Simple Voltage Amplification Issue

Thread Starter

Andrew Burke

Joined Jan 26, 2016
28
I have a 555 timer setup.
Just a simple clock.
Pin Layout is:

8 to VC+
1 to VC-
2 to 6
2 to 1000uf Cap to Ground
2 to 1K pot to 7
7 to 1k Pot to VC+

A Very basic Pinout for a 555 Based Clock.
Lets assume VC+ of 5v

The 555 Output varies depending on potentiometer configuration, but never outputs higher than 3V
I need it to output as close to 5V as I can get it to.
How can I amplify the output signal to have 2V higher output?
 

AlbertHall

Joined Jun 4, 2014
10,018
The NE555 output never gets really close to the supply rails. If you don't need lots of current from the '555 output use the CMOS version, LMC555,
 

dl324

Joined Mar 30, 2015
10,941
It's preferred for you to post a schematic.

How do you have the reset pin connected?

What are you driving with the output?
 

WBahn

Joined Mar 31, 2012
25,910
Sounds like you are using a TTL version of the chip. What is the full part number you are using?

If it is TTL, then it is very common for TTL outputs, when HI, to only be in the 3.0 V to 3.5 V range even when unloaded. That meets the requirement for the minimum HI voltage level for 5 V TTL.

The only way to increase it would be to increase the supply voltage by a couple of volts, to use a comparator (which can be a logic buffer a simple transistor with a pullup) after it that can go to 5V, or to use a CMOS 555 timer, which can generally go to higher voltages, at least when unloaded.
 

Thread Starter

Andrew Burke

Joined Jan 26, 2016
28
The NE555 output never gets really close to the supply rails. If you don't need lots of current from the '555 output use the CMOS version, LMC555,
Unfortunately that doesn't really solve the problem.
I used this as an example. I experience voltage drop in dozens of circuits.

I am using the 555 to create an audio synthesizer.
I don't have the money for school (nor the time) but I have invested thousands in good text books!

However, this one question I cant seem to solve:

How to bring voltage back up to the supply voltage, whilst maintain whatever information is contained there in. In the audio world we do this with an amplifier, and that would be good... but I may need to do this a hundred times or more in my synth... it doesn't seem practical to use a 30 component amplifier every-time I want to boost the the voltage back up. There must be a way to do this.

Also I have 2800 NE555 timers. I have 0
 

Thread Starter

Andrew Burke

Joined Jan 26, 2016
28
Sounds like you are using a TTL version of the chip. What is the full part number you are using?

If it is TTL, then it is very common for TTL outputs, when HI, to only be in the 3.0 V to 3.5 V range even when unloaded. That meets the requirement for the minimum HI voltage level for 5 V TTL.

The only way to increase it would be to increase the supply voltage by a couple of volts, to use a comparator (which can be a logic buffer a simple transistor with a pullup) after it that can go to 5V, or to use a CMOS 555 timer, which can generally go to higher voltages, at least when unloaded.

I kind of understand what you are getting at here. Basically I am using the 555 to drive another 555, and that 555 to drive another 555.
3 555's is the limit with 5v, as the output usually is around 50% of the input.
Whilst, I can increase the voltage to add an additional 555 into the chain... What I am doing requires dozens of chained 555 timers...

I also experience this voltage drop under other circumstances:
Using Diodes, Transistors and various other IC's.
Now I am no professional yet and I realize there is much for me to learn, but this seems to me to be super basic... As far as my growth in the field of electronics goes, to me this seems like the most important next thing to learn.

I keep running into this problem in various circuits.

So regardless of the chip. Say you have a supply voltage of 5v, and somewhere in a circuit a voltage is 3v, what can you do to boost that 3v to the supply voltage.
 

Thread Starter

Andrew Burke

Joined Jan 26, 2016
28
It's preferred for you to post a schematic.

How do you have the reset pin connected?

What are you driving with the output?
I don't connect the reset pin. It seemed redundant so I didnt use it.
Plus I still need to solve the issue regardless of the 555 timer circuit, of being able to boost voltage... heck, if my circuit consists of just an LED the voltage after the LED drops... This is killing me. LOL....

The output is connected to a pair of power insignia speakers, connected by a 1/8" jack
 

WBahn

Joined Mar 31, 2012
25,910
I kind of understand what you are getting at here. Basically I am using the 555 to drive another 555, and that 555 to drive another 555.
3 555's is the limit with 5v, as the output usually is around 50% of the input.
What do you mean by having one 555 drive another. A schematic of what you are trying to do would be VERY helpful!

Whilst, I can increase the voltage to add an additional 555 into the chain... What I am doing requires dozens of chained 555 timers...
Perhaps a much better place to start is not how do you get a 555 timer to do what you want, but rather what is it that you are trying to accomplish in the first place?

It could well be that there is a very simple way to solve your basic problem that has nothing to do with 555 timers or, if it does, that a slightly different approach might work very easily. It's not at all uncommon for people, especially when you have limited experience in a field, to get bogged down trying to figure out how to force a poor approach to work and no one spots it because the basic problem is never even mentioned, only the problem associated with the approach.

It's somewhat like someone asking how to work an extensible mirror in order to see how to position the end of a small, flexible hose. The discussion can go on forever until the person happens to finally mention that the problem they are trying to solve is adding oil to their car's engine and they are trying to work a hose up from underneath the car. At that point someone can offer up a completely different approach to solve the real problem: Open the hood!
 
Last edited:

Thread Starter

Andrew Burke

Joined Jan 26, 2016
28
What do you mean by having one 555 drive another. A schematic of what you are trying to do would be VERY helpful!



Perhaps a much better place to start is not how do you get a 555 timer to do what you want, but rather what is it that you are trying to accomplish in the first place?

It could well be that there is a very simple way to solve your basic problem that has nothing to do with 555 timers or, if it does, that a slightly different approach might work very easily. It's not at all uncommon for people, especially when you have limited experience in a field, to get bogged down trying to figure out how to force a poor approach to work and no one spots it because the basic problem is never even mentioned, only the problem associated with the approach.

It's somewhat like someone asking how to work an extensible mirror in order to see how to position the end of a small, flexible hose. The discussion can go on forever until the person happens to finally mention that the problem they are trying to solve is adding oil to their car's engine and they are trying to work a hose up from underneath the car. At that point someone can offer up a completely different approach to solve the real problem: Open the hood!
I realize there are a million ways to do things correctly in electronics.

But for me the issue is not just with 555 timers.
If a circuit contained just 1 1n4001, connect in bias mode to the supply, the voltage on thr anode would be lower than the voltage at the cathode.

How do I bring the voltage at the anode up to the same level of the voltage of the cathode.
What kind of ic, or transistor can I run connect at thw anode to bring the voltage up to that of the cathode.

Look, maybe I am making it sound more complex than it is.... this should be very beginner electronics. I know it can be done.

Its what happens in an audio amplifier...
the signal coming in can have .01v, yet be driven through speakers at 50v.

Im going to try the resistor idea from above.
 

WBahn

Joined Mar 31, 2012
25,910
How you can do it, and whether you need to or should do it, depends on exactly what you are trying to do!

If I am sending a 5V TTL signal into another 5V TTL gate, then the fact that the actual output from the first gate is 3 V does not matter and I do not have to "bring it up" to 5 V in order to feed it into another TTL gate's input. It does not matter how many gates I cascade, because each gate recognizes the logic level represented by the voltage at it's input and drives the voltage at it's output at a level that can be recognized by the following gates. When operating in a digital world, only the logic levels matter -- specific voltages within those levels don't.

You seem to be thinking that because the voltage output of the first 555 is 2 V below the supply, that the voltage at the output of the second gate is going to be a further 2 V below the supply. That isn't the case. All of the outputs from all of the 555s will be at about 3 V. If you are using the output from one 555 to trigger the next 555, then you don't need to restore a 3 V output to 5 V because the trigger input's threshold (unless you've overridden it with the control input) is at Vcc/3 or about 1.7 V. As long as the output is comfortably above this, the timer won't trigger until it falls below that level. But if you are using the output from one 555 to interact with the timing circuitry of the next one, then you might need to address the voltage level because now you are interfacing a digital output to an analog world and the actual voltage levels matter a lot more.

So. Once again. What, exactly, are you doing that makes you think that you are going to have progressively deteriorated voltage levels as you go from one stage to the next? If that is the case, then it is almost certainly also the case that you are doing something you should not be doing. But we can't tell unless you show us, with a schematic, what it is you are doing.
 

dendad

Joined Feb 20, 2016
3,564
I do wonder why it is so hard to get details from new posters.
Still, if I can figure out what you are after, and that is pretty hard, try using the CMOS version of the 555 as you have been advised before.
http://www.ti.com/lit/ds/symlink/tlc555-q1.pdf
Really you need to put a circuit up and explain what your problem is. In most circuits, the output will not swing to exactly rail to rail. But there are many that come really close to it. You may not need rail to rail swings anyway.
It does seem like going to the CMOS 555 chips will fix it. They require less power and swing further.
Why don't you try one?
 

Thread Starter

Andrew Burke

Joined Jan 26, 2016
28
How you can do it, and whether you need to or should do it, depends on exactly what you are trying to do!

If I am sending a 5V TTL signal into another 5V TTL gate, then the fact that the actual output from the first gate is 3 V does not matter and I do not have to "bring it up" to 5 V in order to feed it into another TTL gate's input. It does not matter how many gates I cascade, because each gate recognizes the logic level represented by the voltage at it's input and drives the voltage at it's output at a level that can be recognized by the following gates. When operating in a digital world, only the logic levels matter -- specific voltages within those levels don't.

You seem to be thinking that because the voltage output of the first 555 is 2 V below the supply, that the voltage at the output of the second gate is going to be a further 2 V below the supply. That isn't the case. All of the outputs from all of the 555s will be at about 3 V. If you are using the output from one 555 to trigger the next 555, then you don't need to restore a 3 V output to 5 V because the trigger input's threshold (unless you've overridden it with the control input) is at Vcc/3 or about 1.7 V. As long as the output is comfortably above this, the timer won't trigger until it falls below that level. But if you are using the output from one 555 to interact with the timing circuitry of the next one, then you might need to address the voltage level because now you are interfacing a digital output to an analog world and the actual voltage levels matter a lot more.

So. Once again. What, exactly, are you doing that makes you think that you are going to have progressively deteriorated voltage levels as you go from one stage to the next? If that is the case, then it is almost certainly also the case that you are doing something you should not be doing. But we can't tell unless you show us, with a schematic, what it is you are doing.
But I am nog using the output of the 555 to trigger the next 555. I am using the output to power the next 555.

During High output of 555a, 555a turns on 555b. During the high output of 555b, 555b turns om 555c.

Triggering doesnt work. It creates many issues.
And as stated above, I do not think it drops 2V, I think the output is about half the input voltage.
I will add "+ or - 1v".

I will add for my 555 concept the resistor did work that was suggested above.

It gets me much closer with some tweaking to the input voltage.

I think i need to search for a really simple audio power amp. I think this might solve my problems since I am dealing mostly in audio.

I plan on passing signals through thousands of analog components. I need a way for that signal to not continue to lose strength..

If I am not making sense im sorry.
 

LesJones

Joined Jan 8, 2017
2,665
What you have just described is easy to solve. Drive the base on an NPN transistor (Or small N channel mosfet.) via a suitable value resistor Connect its collector to the gate of a P channel mosfet via a resistor. Connect another resistor between the gate and source of the P channel mosfet. Connect the source of the P channel mosfet to the positive supply rail. The next 555 would be powered from the drain of the P channel mosfet. There would be almost no volts drop across the mosfet. The choice of mosfet and resistor values would depend on the supply voltage being used. This is not a universal solution to all problems. A solution needs designing for each situation. Using a 555 in this way creates another problem. The period of the first cycle of the waveform will be longer than the rest.

Les.
 

dendad

Joined Feb 20, 2016
3,564
Why do you need to power each 555 from the previous one? That is an odd way to do it.
It would make more sense to just enable the next one. Hook the first 555 output to the next 555 reset.
Even so, going the CMOS route may work your way.
 

WBahn

Joined Mar 31, 2012
25,910
But I am nog using the output of the 555 to trigger the next 555. I am using the output to power the next 555.
You do NOT want to power one 555 from another unless you are extremely careful. If you do this and have a chain of, say, ten 555 timers, that first timer has to power ALL of the other 555 chips. You will quickly run out of drive strength even if they were rail to rail.

If you really insist on using this approach (as opposed to seeing if the hood can be opened ;) ) then the way to do it is to use an inverter and a PFET (or a PNP transistor) to power the next stage. You need the inverter (which can be nothing more than an NFET or an NPN) since the driver transistor requires a LO signal to switch on. You can do it with two transistors and two resistors per stage. You can probably find suitable transistor arrays and resistor SIP packs to keep things small and tidy.

Another way to do it is with buffer ICs, but you need to find one that can provide all of the current needed by the circuitry it is driving (which is just the next 555 stage).

During High output of 555a, 555a turns on 555b. During the high output of 555b, 555b turns om 555c.

Triggering doesnt work. It creates many issues.
What issues? I'm willing to bet that a reasonably simple circuit that does what you need can be done without this cascaded powering approach. But there's no way for us to even attempt to suggest one because you refuse to tell us what you are trying to do.

Powering ICs up and down introduces issues of its own since their behavior is seldom guaranteed during power up and power down. In the case of a 555, you need to be sure that your timing circuits are powered properly and you will probably introduce additional uncertainty in your timings no matter what you do.

And as stated above, I do not think it drops 2V, I think the output is about half the input voltage.
I will add "+ or - 1v".
Test it and see. Power the 555 with 15 V and see what the output is when it is HI. You claim it will be somewhere in the 6.5 V to 8.5 V range. I claim it will be somewhere in the 12 V to 14 V range.

I will add for my 555 concept the resistor did work that was suggested above.

It gets me much closer with some tweaking to the input voltage.
But what happens when you then try to power something via that resistor? If you use even a 100 Ω resistor, then a 20 mA current draw will drag you right back down to 3 V. Also, if you have resistors tied between 5 V and the output of each 555 and use the output of 555 #k to power 555 #(k+1), what happens when 555 #k is not powered? Does it's unpowered output pull the output LO? The answer is almost certainly no. The output likely is the next best thing to floating. That means that 555 #(k+1) is being powered by that pullup resistor, which means ALL of the 555s will be powered by their pullup resistors. But wait, it gets better. As a 555 powers up via the resistor, it is able to pull its output LO, thereby depowering the next one. But as soon as the next one depowers, the one after that powers up via the resistor. The end result, unless you are lucky: chaos!

I think i need to search for a really simple audio power amp. I think this might solve my problems since I am dealing mostly in audio.

I plan on passing signals through thousands of analog components. I need a way for that signal to not continue to lose strength..

If I am not making sense im sorry.
The better route is to solve the underlying problem appropriately. Stop insisting on feeding the hose up from the ground and look for a hood latch!
 
Top