| 摘要 |
<p>An output transistor (T,) to be protected, which transistor supplies a current (Io) to a load (3) is driven by a drivertransis- tor (T2). The base-emitter junction of current-sensing transistor (T2) is arranged in parallel with that of the output transistor (T1), the collector current of this transistor (T3) being a measure of the current (lo) of the output transistor (T,). A current generator (5) supplying a reference current (Iref) is coupled to the collector of the current-sensing transistor (T3). the collector current of the current-sensing transistor (T3) exceeds the reference current (Iref) the protection circuit is activated in that the driver transistor (T2) is bottomed via a transistor arranged as an emitter-follower (T4) so that the base current of transistor T, is limited. Thus, the output current (lo) of outputtransis- tor (T,) is limited to a maximum value which is substantially equal to the product of the reference current (Iref) and the ratio between the emitter areas of the output transistor (T,) and the current-sensing transistor (T3).</p> |
