How does this circuit work

[Andy Brown]

Hello,
I am very interested in how this 200W amplifier circuit works as I am planing to base a college project around this circuit . But I no idea how it works, and I have limited understanding on how the circuit produces the sound required.
The following circuit is the 200W vellemaN K8060 https://www.esr.co.uk/velleman/k8060.htm
This is the manual: https://www.esr.co.uk/manuals/k8060.pdf
Can someone please explain how the circuit works in terms of the components,
Thanks.

 

[ronsimpson]

Are you really wanting to learn how this amplifier works?
OR
Are you wanting me to see the amplifier and pay money for it. Do you work for ESR Components?

Please explain how you will use the amplifier.

 

[Andy Brown]

Are you really wanting to learn how this amplifier works?
OR
Are you wanting me to see the amplifier and pay money for it. Do you work for ESR Components?

Please explain how you will use the amplifier.

I really want to know how this amplifier works, I don't want anyone to go out buying stuff please don't. I will be using the amplifier in a project putting it in a case however one section of the project is to explain how the circuit works. I don't work for esr. I am asking how this circuit works, if you can explain the circuit diagram.

 

[AnalogKid]

If you really have no idea how this works, then you probably are out of your depth. This is not a very complicated amplifier circuit, but it does use several different circuit concepts: input differential amplifier, common emitter voltage amplifier, active zener, complimentary-symmetry output stage, bootstrap current source, and negative feedback. If you don't understand at least the basics of how these functions work, an overall explanation of the amplifier probably will not tell you much.

ak

 

[Andy Brown]

If you really have no idea how this works, then you probably are out of your depth. This is not a very complicated amplifier circuit, but it does use several different circuit concepts: input differential amplifier, common emitter voltage amplifier, active zener, complimentary-symmetry output stage, bootstrap current source, and negative feedback. If you don't understand at least the basics of how these functions work, an overall explanation of the amplifier probably will not tell you much.

ak

I currently learning electronics have a good understanding on how transistors work and ext however I have no idea how to explain it. Thank you fore listing these concepts, I will research these concepts. Is there anything else that I need to explain?

 

[ronsimpson]

This is only a small piece. "Emitter follower" T8
Voltage gain is 1. Current gain is very high.
-------------
Current limit:
Current flows from +40V to output. R19 is used to measure this current. If the voltage across R19 is too big then T4 base to emitter will have 0.65 volts and turn on. When T4 turns on, it turns T8 off and limits the current.
----------
There is another emitter follower just below this one. It pulls down to -40V.

 

[Andy Brown]

Thank you very much ! Love the help

 

[ronsimpson]

A normal transistor needs 0.6 to 0.7 volts B to E for the part to turn on.
A Darlington transistor is two transistors in one. It takes twice as much voltage to turn on.
A diode = about 0.65 volts. So some of us say D=0.6 volts. 2D=1.3 volts.
T8 and T7 need 2D to turn on. We need both T7 and T8 to be almost on. So 4D plus a small amount is from T7 base to T8 base.
T6 makes this voltage.
------
If the output of the amp is zero volts then T8-base is +2D. (0+1.3V) And T7-base is -2D.
If the output of the amp is 5V then T8-base is 5+1.3V and T7-base is 3.7V.
------
ask questions!

 

[bountyhunter]

Hello,
I am very interested in how this 200W amplifier circuit works as I am planing to base a college project around this circuit . But I no idea how it works, and I have limited understanding on how the circuit produces the sound required.
The following circuit is the 200W vellemaN K8060 https://www.esr.co.uk/velleman/k8060.htm
This is the manual: https://www.esr.co.uk/manuals/k8060.pdf
Can someone please explain how the circuit works in terms of the components,
Thanks.

Hello,
I am very interested in how this 200W amplifier circuit works as I am planing to base a college project around this circuit . But I no idea how it works, and I have limited understanding on how the circuit produces the sound required.
The following circuit is the 200W vellemaN K8060 https://www.esr.co.uk/velleman/k8060.htm
This is the manual: https://www.esr.co.uk/manuals/k8060.pdf
Can someone please explain how the circuit works in terms of the components,
Thanks.

Actually, it's a 100W RMS (four Ohms) and 70W RMS (eight Ohms) amplifier.

It's a pretty standard amplifier circuit..... with a lot of shortcomings. If you are building something for home usage, you may want to consider building up a design using an integrated amplifier device like this:

https://www.ti.com/lit/ds/symlink/lm4780.pdf

**broken link removed**

This one can be bridged to provide 120W RMS into an eight Ohm load (single channel), or run as a stereo amp at 60WRMS per channel..

Aside from simplicity, integrated solutions have some real advantages:

1) They have a simple soft start feature that eliminates the THUMP that can damage speakers at turn on and turn off.

2) The entire circuitry is thermally connected so it all tracks thermally, which means the output bias current is stable. If you investigate the design you'll find out how and why that weakness kills this type of circuit.

3) The device has built in thermal shutdown which will save it in cases where it is accidentally overloaded or just run too hard.

Anyway, when I built the amp to drive my TV speakers, I used an integrated device like this.

 

[ronsimpson]

The amplifier's output should look just like the input but "louder".
T1 & T2 compares "in" and "out/300". If there is a difference it is amplified and sent to T3 which amplifies more.
-----------------
I made the amp more simple. How this helps.

 

[Andy Brown]

Thank you very much. Antother question is what part of the circuit can I breadboard doesn't need to be the whole circuit.

 

[alec_t]

You could breadboard any part of the circuit, depending what your aim is.

 

[ronsimpson]

what part of the circuit can I breadboard

T7 & T8 will get hot. They need to be connected to a heat sink.

 

[ntetlow]

Hello. I've jusI come across this thread. I've bought the parts for the Vellman K8060 and will be assembling it soon. Firstly I wanted to simulate the circuit in LTSPICE. Being fairlly green, having run the simulation I couldn't see what those transistors were used for until I came across some precautionary info and consequently stumbled on this thread. Could you please tell me how I could simulate the situation in my schematic where the precaution kicks in and the two darlington pairs switch off?

 

[alec_t]

Welcome to ETO!
1) You have hijacked someone else's thread. It's always better to start your own (it's good manners and you can add a link to a previous thread if appropriate).
2) You are 'necro-posting' in a 4 year old thread (participants may have lost interest in it).
3) What 'precaution' are you talking about and which particular transistors? We're not mind-readers.
4) If you have already tried simulating the circuit please post your .asc file.

 

[ntetlow]

In th simulation attached of the amplifier K8060, Q7 and Q5 are used to turn on if the current to the darlington pairs U1 and U2 gets too large, thus cutting off either of U1 or U2.
What I would like to do is change the simulation temporarily to reproduce such an occurance. Could someone suggest a way of doing this?
I apologise for not creating a new thread for this question but I thought it might be easier to refer to the previous replies on this very subject.

 

[alec_t]

Could someone suggest a way of doing this?

Increase the value of R11 dramatically.

 

[ronsimpson]

I would put a 2 ohm resistor from output to ground. OR 1 ohm.
(normally audio amp load is more like 8 ohms)

 

[ntetlow]

I increased the value of R11 to 20k. This started Q7 and Q5 but the D pairs U1 and U2 did not cut off. So half the trick done, any more suggestions greatly appreciated.

 

[Nigel Goodwin]

I increased the value of R11 to 20k. This started Q7 and Q5 but the D pairs U1 and U2 did not cut off. So half the trick done, any more suggestions greatly appreciated.

I don't see as R11 has anything to do with it?, as ronsimpson said stick a 2 ohm or 1 ohm resistor (I'd go for 1 ohm) on the output, monitor the output with the onscreen scope, and gradually turn the input up and see what happens - I would expect the output to start clipping before it normally would.

No idea what your transistor references are, as the circuit use T.