Push-Pull world


1 0mA current regulator?

　　Firstly 0mA current regulator is given. NPN transistor has a feature like this.





　　Select R1 and R2 for Vbe to be 0.48V.




　　Next PNP transistor's regulator is given in a same way




　　Let them bind together.



　This is a fundamental form of class B push-pull circuit.




　　Probably voltage-current curve will be like this.(What a distortion!)

　Note) Actually 100% current feedback is operated, this curve will be linear.
　　　　　Curve like that realizes on the circuit below.
　　　

2 The effect of 100% current feedback

　　In such a class B push-pull circuit




　　Vbe=constant



　Input-output curve will be this way. But it is unsatisfying.

　I'll try to explain by current feedback way of thinking.

　　Firstly assume RL=8Ω, and draw a line of R of 8Ω inversely.

　　 Secondly when Vin increases from a to c, the cross point indicates Vbe and Ic.




　　Now,
　　Vout=Vin-Vbe

　　So we transfer Vin to Vout's side(green line ay')

　　And substract Vbe from that(xx',yy')

　　Vout appears as a curve binding a,x,y.
　

　　This is an example in a case of k1056

3 Complementary circuit




　　This circuit is one that systhesizes single current from two collector current.
This circuit has a gain.




　　This circuit is emitter follower that has a bias well-designed. This is used as a
input buffer or as a final stage.

　　These circuits can be connected freely for they have single-end input and output.






　　This is a power amplifier. I call an amp of this type as Single coupled push-pull
amp.

4 Balance drived amp




　　Each stage is combined by balanced-drive . I call an amp of this type as
Balance coupled push-pull amp.

5 Mixed type


a)Complementary push-pull amp is pure single-end coupled amp.

b)Kaneta method's symmetrical amp is a pure balance-drive push-pull amp.

c)Kaneta method's GOA amp is a mixed type of both.






　　In case of this amp first stage and second stage are coupled directly.
Circuit is very simple, but good complementary pair is difficult to find.





　　This is Kaneta method's symmetrical amp. Pair-matching of the parts is
superior to complementary pairs.




　　This is a simplified form of Kaneta method's DC amp called GOA.(cascade
transistors are omitted).

　　1st and 2nd stage are balanced type, 3rd stage is a single-end type.


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