amplify the signal output of the 555 timer

[maxima_diesel]

how would you amplify the output signal of a 555 timer without distorting the signal? i tried using a bc547 transistor and the output voltage is increased from 150 mV to approximately 700 mV. I want the output to be around 2-3V. Also the amplified output signal from the transistor became distorted and is not the 40kHz pulses that I wanted anymore. any suggestions?
thanks a lot

 

[keith1200rs]

There is something wrong with what you have built if you only get 150mV out of the 555. Show your schematic.

Keith

 

[maxima_diesel]

there, that is the schematic. thanks for your reply

 

[goldsmith]

Hello
At first i agree with keith . and at second , how much is the value of your VCC ? and if you want it's square wave out put , you shouldn't use a simple transistor . you should use a totem pole . because of the bad behavior of single transistor at this case .
Regards
Goldsmith

 

[maxima_diesel]

hi, thanks vcc is at 5 volts and my circuit is the same except that i didnt use a button to the output. can you please elaborate what a totem pole would do? thanks for the reply.

 

[goldsmith]

The totem pole is simply 2 transistor that combined together , a first transistor will charge the load ( give it voltage ) and another will discharge it ( will connect it to the ground when the time of operation is over . and it will provide a good square wave .
and you should increase the supply voltage . e.g about 10 volt.
Regards
Goldsmith

 

[maxima_diesel]

The totem pole is simply 2 transistor that combined together , a first transistor will charge the load ( give it voltage ) and another will discharge it ( will connect it to the ground when the time of operation is over . and it will provide a good square wave .
and you should increase the supply voltage . e.g about 10 volt.
Regards
Goldsmith

thanks for your reply goldsmith, is it ok if u can give a website or post an example schematic of a totem pole transistor configuration? it seems that there is not a lot on google. i might keep the supply voltage to 5V i think for convinience and the 555 timer is powered by 5 volts anyway.
thanks again

 

[mister_rf]

See here:

 

[keith1200rs]

I don't see the relevance of discussions of totem pole circuits. The 555 can source 100mA from 5V supply although you will only get around 3V peak not 5V. I think you have to look for building errors, short circuits etc. The only thing I can see that is wrong is the missing 10nF that should be on the control voltage pin.

Keith

 

[goldsmith]

See below please:
Push


Dear Keith
As we know if he try to amplify the square wave with a single and simple transistor , the out put will have large value of DC ( will shift up more than past ) . and if we use a totem pole . all things will be right .
Regards
Goldsmith

 

[keith1200rs]

Goldsmith,

While he is trying to amplify the signal from the 555, the signal is not correct in the first place. It should need no amplification. It should be more than 150mV. The true cause of the problem needs finding and fixing.

Keith

 

[goldsmith]

Dear Keith
Yes i'm agree with you . i didn't see this very low value of amplitude for 555 IC until know and i think a mistake is occurs with his circuit building .
Regards
Goldsmith

 

[maxima_diesel]

thank you for all your replies again. i shall double check my circuit and find the fault in it. i will update this post once i've found a fault. thanks again to goldsmith, keith and mister_rf. should i just rebuild the same circuit that i posted on here or any of you guys have a suggestion for a better 555 timer circuit? if so can u please post the schematic on here? thanks again for your help

 

[keith1200rs]

The circuit is fine. If you powered it from more than 5V then you would have more accuracy in setting the LED current, although that could be improved at 5V with a single transistor buffer if required anyway.

Keith

 

[maxima_diesel]

The circuit is fine. If you powered it from more than 5V then you would have more accuracy in setting the LED current, although that could be improved at 5V with a single transistor buffer if required anyway.

Keith

ok thanks. i tried increasing vcc to 7V but the output signal pulses get distorted, what ever value i change the potentiometer to, the frequency would not change at all.. so i think the circuit is optimised for 5 V. are u suggesting that i shud use a buffer for the output of the IC? or to increase vcc? i just use a power supply for the vcc so using a transistor is not necessary to increase it.

 

[goldsmith]

Agai Hi
What is your load resistance ? perhaps it is higher than the allowable value . or maybe your IC isn't intact . try to change your IC
Regards
Goldsmith

 

[keith1200rs]

Try the circuit with no load and see if it works OK then.

Keith.

 

[maxima_diesel]

hi, i realised the mistake, and i corrected it, the output voltage is now 1V Vpp but i dont think the current this time is high enough, because when i use my camera to see how bright the led is, its barely lit. I used Vcc as 9V as suggested as well. My setup now has no load resistance. When I tested it, with my receiver circuit, the receiver detects the pulsed ir output occasionally. what can u guys suggest to increase the output current this time? to make the IR LED brighter , hence emit more IR radiation? thanks for your replies

 

[keith1200rs]

Are you using this to drive an LED for a camera light source? If so, why? You will get aliasing between the camera shutter speed and the LED modulation. Simply drive the LEDs continuously. Also, what colour are your LEDs and is it a monochrome camera? White LEDs have a high forward voltage.

Keith

 

[maxima_diesel]

no im not using it to drive an led for a camera. im creating an ir emitter and receiver circuit. im using my camera to see how bright the ir emitter is because i cannot measure the current through it. another weird thing i found is that with my current set up the ir emitter led only works when connected in reverse polarity, meaning the long side of led to ground and short side to the output of 555 timer. if i connect it the other way the circuit gets shorted. im not too sure why.