Effect of output Stage Configuration on Damping Factor

[Workhorse]

Hi everybody,

recently I build these 2 type of output stages and found out that one has a greater damping factor than the another...although these are using same transistors in them and same idle current per stage 6mA -> 45mA -> 100mA

Is'nt that the base to emmiter junction when tied with resistor improves the damping factor of the stage.....

what is the reason, kindly help me.....

regards,
K a n w a r

[pb]

Current gain of the right stage is greater thus assuming the same source impedance,
the eventual ouput impedance (roughly Zinput/gain) will be smaller: better damping factor.

On the other hand left stage should be faster.

Cheers,
Przemek

[jcx]

I would guess the effect of the topological difference is less than the hfe mismatching if you didn't specifically sort/match similar transistors between the circuits

also most people today would bias the pre/driver stages with a series R between each complementary pair of emitters to avoid turning off the pre/driver and improve commutaion of the output stage

[Workhorse]

Thanks everybody for the information.....

Przemek, how would you conclude that the current gain of right stage is higher when using same devices as used in others...


regards,
K a n w a r

[ilimzn]

I'm not Przemek, but I would say this is because none of the Ie of the driver transistors is 'stolen away' to feed the load through the resistors tied to the output as on the left side.