GB1013412A - Asymmetrical push-pull amplifier stage for stereophonic signals - Google Patents

Abstract

1,013,412. Stereophonic systems; sliding bias amplifiers. TESLA NARODNI PODNIK. June 29, 1964 [June 29, 1963 (2)], No. 26790/64. Headings H3T, H4J and H4R. An asymmetrical push-pull amplifier stage for stereophonic signals comprises, Fig. 3, a pair of similar amplifying elements V 1 and V 2 connected in series across a power supply B 1 , B 2 . The stereophonic channel signals are applied, one direct to element V 1 and the other in reverse polarity to V 2 , it is shown that between tapping a and the centre tap S of the transformer connected in series between the amplifying elements appears one channel signal while the other channel signal appears between the tap b and the centre point S. A sum signal may be obtained between the centre tap S and the centre tap of the power supply O. Negative feedback may be taken from points Zp and Zl and the valves V 1 and V 2 may be replaced by common emitter transistor amplifiers, Fig. 4 (not shown). The outputs from additional windings on the transformer Tp may be rectified and fed back to vary the bias on the amplifying elements so that while no signal is passing they are biased in class B but as soon as a signal is present the bias is changed to class A. The bias may be applied direct to the output amplifier elements. Fig. 5 (not shown) or to previous amplifier stages of c coupled to the output elements as shown for the driver stage Q 4 , Fig. 6.