power amplifiers class a

[Disha Karnataki]

hello,
here is the link about transformer coupled class A power amplifier i am not getting what is the author exactly trying to convey in his 4th para under the subtitle CLASS A AMPLIFIERS
https://mysite.du.edu/~etuttle/electron/elect26.htm




if at all could not find that para please intimate

 

[ud23]

it is explanation about the shunt type connection of your load.It explain if your load DC current not matched then you can use the capacitor in the series of your output load which is actually used to blocked the DC current which is actually passing through the transformer .so for connecting your load output in parallel connection specially when it is transformer coupled load u need one of kind capacitor to blocking unwanted DC current which coupled in the series connection of load .and for maximum swing u choose resistor value which brigs your collector output voltage half of the addition of supply voltage and base voltage.

 

[Disha Karnataki]

he has also mentioned that whether the transformer is capable to handle dc or no can be easily understood just by looking at the transformer i.e if the x'mer is center tapped then it's not capable of handaling dc & if it's normal x'mer(other than center tap) then it's capable of handaling dc..
how is this ??? i mean how will u explain this??

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is this the para u read::
""""You may have been surprised to find the voltage amplitude at the collector to be greater than the supply voltage of 12V. This is the result of the transformer, which carries the collector as much higher than 11 V as it does below it. The base voltage rises to 2.2 + 1.3 = 3.5 V, and the difference between this and 11 V is 7.5 V. The collector can sink only about 0.5 V farther before the transistor saturates, so this is the limit of the ouput excursion, exactly what I measured. The transformer makes the 12 V supply act more like a 24 V supply as far as output is concerned, which is a great advantage of transformer coupling""".



i guess u read the para of shunt feed class a amplifier

 

[crutschow]

he has also mentioned that whether the transformer is capable to handle dc or no can be easily understood just by looking at the transformer i.e if the x'mer is center tapped then it's not capable of handaling dc & if it's normal x'mer(other than center tap) then it's capable of handaling dc..
how is this ??? i mean how will u explain this??

......................................

His assumption apparently is that an audio transformer with a center-tapped primary is designed for a push-pull (class B) stage which passes little or no DC current through the transformer, and that a transformer with a non-center-tapped primary is designed for a single-ended (class A) stage which does pass DC through the transformer.

 

[Disha Karnataki]

His assumption apparently is that an audio transformer with a center-tapped primary is designed for a push-pull (class B) stage which passes little or no DC current through the transformer, and that a transformer with a non-center-tapped primary is designed for a single-ended (class A) stage which does pass DC through the transformer.

yes i got your point that he means to tell us that it is push pull class b amplifier.
but how is that it doesnot passes dc current through transfromer???? This point didnot convince me...

 

[chuckey]

The secret is the centre tap. The DC current flowing from the centre tap out to each end, produces two magnetic fields that cancel, so the real magnetic field is zero, other then the AC signal component. This is why the shunt fed transformer is used, the series capacitor keeps the DC out of the transformer. In real life in the 1960s, the driver transformers used to be designed to have the DC current flowing through their primary, with a centre tapped secondary to feed the two output transistors.
Frank

 

[Disha Karnataki]

the two mmf created are canceled as there are in opposite directions to the primary of the x'mer.
But, these currents are got out from transistor collectors(one is NPN & other PNP) passing the collector current through the resistance this is the sinusoidal audio signal formed right??? You mean this is allowed to pass through the x'mer??