| 摘要 |
An amplifier of differential type such as a comparator or operational amplifier has two input terminals (1, 3) which are formed by the base terminals of input, amplifying transistors (T1, T2) of for example npn-type. The collectors of the input transistors are connected to some supply voltage (VCC) through for example a current mirror circuit (T4, T5). The emitters of the input transistors are through a transistor (T3) connected as a current generator connected to another supply voltage (VEE) close to ground potential. The base-emitter-junction in the input transistors are protected by protective transistors (T6, T7) which are connected as diodes, the emitters and bases of which are connected to each other. The effective pn-junction in the protective transistors is then the junction between the base and collector which normally has a larger breakthrough voltage then the pn-junction between the base and emitter. A protection of the input terminals of the amplifier is thereby obtained which can in a simple way be accomplished in for example integrated circuits. Then, the protective transistors are made in substantially the same way as the input transistors and have substantially the same electrical properties as they.
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