Improvements in or relating to transistor circuits

859,322. Transistor circuits. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Oct. 18, 1957 [Oct. 20, 1956], No. 32013/56. Class 40(6). In a chopper or clamping circuit of the type comprising a transistor having its collector connected to a fixed potential, its emitter connected to signal input and output terminals and its base connected to a switching potential source, a circuit is connected between the switching source and the base to ensure that the base can only be switched from the fixed potential in the direction which renders the transistor conducting. In Fig. 3, the emitter-collector path of a transistor T1 shunts the path between the circuit input terminal 1 and the input terminal 3 of an amplifier. A negative input voltage at a switching input terminal 1 will render the transistor fully conducting while a positive potential will render it non-conducting. In the latter condition a network D1, R3, R2 prevents the base from rising appreciably above earth potential. As the input voltage is only very small the collector base and emitter terminals are then at substantially the same potential and almost no leakage current flows. The bottoming voltage which exists between emitter and collector when the transistor is conducting may be eliminated by injecting a small voltage between collector and base when the transistor is conducting. The Provisonal Specification also describes a D.C. amplifier (Fig. 5) in which the collector loads are of such a value that the base potentials of all transistors are equal. The collector-base potentials are therefore zero, but useful amplification may still be obtained. Negative feedback through resistors R7 and R8 is provided to stabilize the operation and a de-coupling circuit R10, C1 may be included in the feedback circuit to prevent feedback of alternating current signals. The base of the first transistor may be connected through a resistor R9 to an HT source in order to provide the desired value of output current.