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Sziklai pair connection

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amriths04

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dear friends,
we all know that when the emitter of the 1st transistor is connected to the base of the 2nd, the 2 transistors together acts as a current booster(darlington). will it also be correct if the collector of the 1st transistor is connected to the base of the 2nd? is there anything wrong?

thank you in advance,
AMRITH.S.
 

darlington

Google "Sziklai" and "Sziklai pair".
 

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    amriths04

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Re: darlington

You can very well use it. But it is not a darlington connection, since the nice thing about darlington is that it gives you another 3 terminal device which acts like a bipolar transistor of higher beta. and double Vbe.
If you use the collector to connect to the base of the next it is effectively having a 2 stage circuit, and you may have problems in frequency response of the circuit by creating a pole at the base because of the really high impedance at that node.
Also the transistor pair cannot be similar type 1 will be npn and thee other will be pnp.
 

Re: darlington

You can use 2 transistors connected the C pin of the 1st to the B of tne 2nd. But this circuit using 2 different transistors, one is pnp, and one is npn.
Then, the E pin of the 1st is connected to C pin of the 2nd.

I never heard about the name of the circuit, but it behaves just like the first transistor, and the second is the current booster/hfe booster.

nguyennam
 

Re: darlington

nguyennam said:
You can use 2 transistors connected the C pin of the 1st to the B of tne 2nd. But this circuit using 2 different transistors, one is pnp, and one is npn.
Then, the E pin of the 1st is connected to C pin of the 2nd.

I never heard about the name of the circuit, but it behaves just like the first transistor, and the second is the current booster/hfe booster.

nguyennam
Click to expand...
The name is "Sziklai pair", or "complementary Darlington", or "compound Darlington". It has near-unity gain like the Darlington, but, due to the feedback, the low-frequency output impedance is lower, and it can have bandwidth and stability issues.
 

Re: darlington

Thank you 10kangstroms,

I love this circuit and have used it very commonly, while rarely use a Darlington circuit, but never know its name.

nguyennam
 

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