If the voltage swing at the output exceeds the power supply voltage levels, which could happen with an inductive load, the top diode clamps the Vout to +Vsupply +0.7v
Or if a negative going transient which exceeds -Vsupply the lower diode clamps the Vout

Do you follow that OK.?

Not exactly...I didn't follow it...please elaborate....

also what kind of protection is provided by clamping the output voltage..
sorry but couldn't relate...

 

Snubber diodes clamp the kickback to the supplies when an inductive load is switched. This is done to protect the switch.

When MOSFET drivers are used, some have sufficient built-in protection and don't need an external snubber.

Snubber diodes also know as flyback diodes are use to short out the excess current generated due to back emf in relays present in the switches
but here it doesn't seem that they are doing any kind of flyback action as eric said....and if they might be doing any kind of snubber action then they might directed towards ground ..in order to short out whole current to ground...But it doesn't seems to be the case..

 

PS - thanks for changing your avatar. It kept reminding me of a guy who used to be a politician in some country; and I'd prefer to forget about him...

Its quite flattering to know that the TS looks like a famous politician of a country ...No problem you let the cat out of the bag ...but only in ears....

 

Not exactly...I didn't follow it...please elaborate....

also what kind of protection is provided by clamping the output voltage..
sorry but couldn't relate...

Exactly which part you don't understand ? This diodes prevent the output voltage to grow beyond supply voltage as a result of flyback from an inductive speaker load.

Snubber diodes also know as flyback diodes are use to short out the excess current generated due to back emf in relays present in the switches

Excess current ??

and if they might be doing any kind of snubber action then they might directed towards ground ..in order to short out whole current to ground...But it doesn't seems to be the case..

To ground ? Why? Also notice that when you flip the diodes you will short the voltage rails. And if you connect the diodes between the output and ground, this will short the output.

 

Snubber diodes also know as flyback diodes are use to short out the excess current generated due to back emf in relays present in the switches

The diodes will clamp voltage spikes from back EMF from any inductive load; including speakers. The spikes can be shunted to any supply that has filtering; not just ground.

 

Its quite flattering to know that the TS looks like a famous politician of a country ...No problem you let the cat out of the bag ...but only in ears....

Actually, it's not flattering for any person to resemble your previous avatar The person I'm thinking of (and I really don't want to think of him) has enough facial similarities that they could be closely related...

 

Actually, it's not flattering for any person to resemble your previous avatar The person I'm thinking of (and I really don't want to think of him) has enough facial similarities that they could be closely related...

but anyway i want to know whos this personality....

 

but anyway i want to know whos this personality....

Can you guess from this?

 

Exactly which part you don't understand ? This diodes prevent the output voltage to grow beyond supply voltage as a result of flyback from an inductive speaker load.

earlier i misunderstood the fact that reverse current that is generated due to back emf must return back to the power supply ..I thought that it should be sinked to ground which was though wrong because in this attempt we have to shunt the load via a diode which will then short the load ..which is obviously undesired...

now the part which i don't understand is how the output voltage is getting clamped in absence of diode...??

sorry to be a little naive..

 

Can you guess from this?
View attachment 89612

can i take an opinion poll on this...

 

can i take an opinion poll on this...

Just don't attribute it to me...

 

now the part which i don't understand is how the output voltage is getting clamped in absence of diode...??

Do you mean without the diode ?? If so, how can you have any clamping if diodes was removed from the circuit.

 

now the part which i don't understand is how the output voltage is getting clamped in absence of diode...??

Do you mean clipping when the dynamic range of the signal exceeds that of the amplifier stage?

 

Do you mean without the diode ?? If so, how can you have any clamping if diodes was removed from the circuit.

i am sorry ..its a typo ...

also you can take it this way,,,that we are talking about power amplifier for audio applications...and to drive a speaker ac signals are required...hence if the output voltage is getting clamped ...as eric in previous post said...it means a dc component is being restored...as clampers are also know as dc restorers...and this dc offset is not useful for audio applications..then whats the whole story is about...?????

 

Do you mean clipping when the dynamic range of the signal exceeds that of the amplifier stage?

no not clipping.....but how the output voltage is getting clamped in presence of inductive load...

I ve heard that a capacitor is required along with a diode to clamp the voltage ...just want to relate it with an inductor..

 

and this dc offset is not useful for audio applications..then whats the whole story is about...?????

Those two diode at the output are there for protection purpose only in order to protect the output transistors. When something strange happens at the output. For example when the output "relay" contacts are de-energized the arc can occur or back EMF can be induced at the output by inductive loads if the amplifier is driven into clipping. But in normal situation those two diodes are OFF. And the speaker is "heavily" damped by low output resistance. Also this type of a protection is not very common in real world audio power amplifiers.

 

Those two diode at the output are there for protection purpose only in order to protect the output transistors. When something strange happens at the output. For example when the output "relay" contacts are de-energized the arc can occur or back EMF can be induced at the output by inductive loads if the amplifier is driven into clipping. But in normal situation those two diodes are OFF. And the speaker is "heavily" damped by low output resistance. Also this type of a protection is not very common in real world audio power amplifiers.

one last question ..about the utility of lower diode??...since the voltage spike due to back emf are shunted into power supply by the upper diode??? then why lower is used..

 

one last question ..about the utility of lower diode??...since the voltage spike due to back emf are shunted into power supply by the upper diode??? then why lower is used..

I have explained the action of the lower diode in post #18, it clamps the negative swing to -Vout -0.7v.

If the voltage swing at the output exceeds the power supply voltage levels, which could happen with an inductive load, the top diode clamps the Vout to +Vsupply +0.7v
Or if a negative going transient which exceeds -Vsupply the lower diode clamps the Vout

 

I have explained the action of the lower diode in post #18, it clamps the negative swing to -Vout -0.7v.

If the voltage swing at the output exceeds the power supply voltage levels, which could happen with an inductive load, the top diode clamps the Vout to +Vsupply +0.7v
Or if a negative going transient which exceeds -Vsupply the lower diode clamps the Vout

ok i got it....