Patent GB-899407-A (GB)
Title: Improvements in or relating to circuits for the successive amplification of a numberof voltages
IPC: H03K17/62
Filed: 1959-10-28
Abstract: 899,407. Transistor circuits; gating circuits. PHILIPS ELECTRICAL INDUSTRIES Ltd. Oct. 28, 1959 [Oct. 31, 1958], No. 36569/59. Class 40(6). [Also in Group XL(b)] Voltages applied from terminals 1, 2. .n to the base inputs of push-pull pre-amplifiers I, II,..N are connected in succession to a common push-pull amplifier 16 by means of a trigger chain of transistors 7, one for each preamplifier, which conduct in turn to render the associated pre-amplifier operative by providing a connection through the emitter-collector path for the common amplifier emitter circuit 5, 6 to a positive supply +E. The pre-amplifier collector outputs comprise common resistors 11, 12 which may either be fed directly or preferably (as illustrated) via a common base push-pull circuit 9, 10 whose low input impedance allows for the appreciable collector capacitance of the pre-amplifiers. Negativegoing impulses introduced during the switchover from one pre-amplifier to the next may be eliminated by limiting diodes 18, 19 and/or a transistor stage 32 which functions to produce suppression pulses of opposite polarity across common collector resistor 13. Resistors 6 are of high value compared with the interval emitter resistances. Potentiometers permit the pre-amplifier circuits to be balanced. In the chain of transistors 7, when a stage cuts off it applies a negative potential via capacitor 29 to trigger on the succeeding stage, the stage remaining conducting until the capacitor has charged sufficiently to bring the base positive with respect to the emitter. A diode 31 suppresses the positive going pulse applied via capacitor 29 when a stage conducts again. The chain may be completed as a ring so that it cycles continuously by placing switch 20 in its upper position so as to connect the collector of the last stage to the base of the first. Alternatively the switch may be placed in its lower position where it connects the chain to a source of clock pulses 21. The emitter circuits include a common low-value resistor 8 across which pulses appear as the chain steps. The pulses may be shaped in integrating and differentiating network 36-39 and employed to trigger a transistor stage 35 whose output is reversed in polarity in stage 41. The final pulses are timed to occur within the intervals when the pre-amplifiers are fully operative. The pulses may be applied to the main amplifier 16 and employed to switch off a stage during the intervals when the preamplifiers are switching from one to the next so as to eliminate the negative-going impulses referred to above. In this respect there is also described a sampling circuit, Fig. 4, which is connected between the output 60 of one stage and in the input 61 of a succeeding stage of the main amplifier and is controlled by the pulses from the trigger chain. The pulses are applied to winding 51 of transformer 50 (the secondaries 52 and 53 of which are centretapped) and are effective to render conducting all of diodes 54, 54<SP>1</SP>, 55, 55<SP>1</SP> whereby capacitors 63 and 64 acquire potentials corresponding to the signals at output 60. The potentials are maintained at the input 61 of the succeeding stage until the next pulse, the diodes remaining cut off between pulses due to potentials held on CR combinations 56, 57; 58, 59; 56<SP>1</SP>, 57<SP>1</SP>; 58<SP>1</SP>, 59<SP>1</SP>. U.S.A. Specification 2,666,868 is referred to.