upper limit of the gain of a darlington pair

[abbey]

darlington pair

Does anybody know if there is an upper limit of the gain of a Darlington pair??For example,if b1=100 and b2=250,is it possible to have a darlington pair with gain β=100*250=25000??

 

[jasmin_123]

Re: darlington pair

Darlington configuration is used to increase the input impedance of a single transistor. Why to care about its current gain?

 

[Audioguru]

Re: darlington pair

Does anybody know if there is an upper limit of the gain of a Darlington pair??For example,if b1=100 and b2=250,is it possible to have a darlington pair with gain β=100*250=25000??

Maybe.
If the currents are enough (the current in the first transitor is very low so its gain will be fairly low), if the current in the second transistor is not too high and if both transistors have a gain that is higher than typical.

 

[karesz]

darlington pair

Hi abbey,
is a (MOS)FET not simpler to use for "current ampifying?
K.

 

[abbey]

Re: darlington pair

i asked that because I was just wondering about the maximum current gain that a darlington pair can have...

 

[Audioguru]

darlington pair

Many ordinary transistors have their minimum and typical gain listed at certain currents but not their max current gain. Most people and circuits do not care about the max current gain.

 

[FvM]

darlington pair

Maximum current gain isn't a specified parameter. Typical gain of small signal darlingtons, e.g. BCV27 is 60000 (@ Ic =0.1..100 mA), minimum gain 20000 (@ Ic=100 mA).

 

[LvW]

Re: darlington pair

Does anybody know if there is an upper limit of the gain of a Darlington pair??For example,if b1=100 and b2=250,is it possible to have a darlington pair with gain β=100*250=25000??

Of course, it is possible. Theoretically!
However, be aware of the consequences! The parameter which determines the voltage gain is the transconductance! Start with the maximum allowable current of the second stage and compute the transconductance of the first stage for a composite current gain of 25000! Perhaps you will be surprised.