Transistor amplifiers

1,017,392. Transistor amplifying circuits. ROTAX Ltd. March 26, 1962 [April 6, 1961], No. 12335/61. Heading H3T. A long-tailed pair comprising transistors 5, 8 connected as shown in the Figure has its output impedance increased by increasing the effective impedances of resistors 3, 4, 6, 7, by connecting transistors 19, 20 of opposite conductivity type to transistors 5, 8 in the manner shown. Resistances 3, 4 and 6, 7 may be replaced by single resistances in which case a tapping of the two single resistances is connected to the bases of NPN transistors 19, 20 respectively. If the resistances of the circuits between the emitters of transistors 19, 20 and terminal 1 are slightly less or equal to the resistances of the circuits between the bases of transistors 19, 20 and terminal 1 then the effective impedances of resistors 3, 4 and 6, 7 are increased. Resistors 23, 24, 25, 26 may be omitted and capacitors 17, 18 replaced by a direct connection. Part of the emitter impedance of the long-tailed pair comprises transistor 11.