| 摘要 |
<p>The operational amplifier (p1) is provided with a feedback loop containing an element, controlled by a separate voltage limiting circuit, e.g. a FET (p5) with variable channel resistance, so as to control the amplification ratio of the operational amplifier (p1). The feedback loop may also include a further amplifier (p3) which allows the voltage limit to be present to a different value in dependence on the polarity of the output of the operational amplifier (p1). A switch (b1) may be provided to allow the voltage limiting circuit to be selectively brought into operation, or the FET (p5) itself may be used to block the voltage limiting circuit.</p> |
