| 摘要 |
<p>PURPOSE:To detect and hold an offset current when signal processing is performed in current mode by holding an interbase emitter voltage corresponding to the peak value of a current and the voltage drop across a resistance in a capacitor, and providing a transistor (Tr) which is controlled with its capacitor voltage. CONSTITUTION:Transistors (Tr) Q1 and Q2, and Q6 and Q7 constitute current mirrors and mutually equal currents flow. Then a current flowing to the Tr Q1 is controlled by a phototransistor (Pt) Q0 and a current flowing to the Tr Q3 is controlled by a 1st constant current circuit 1 and the Tr Q2. The same current as the current IP of the Pt Q0 flows to the Tr Q2, so a current I0-IP flows to the Tr Q3 and a voltage corresponding to the peak current value of the Tr Q3 is therefore charged and held in the capacitor C. Then a current I5 flowing to the Tr Q5 becomes equal to the peak current I0-IP, a current I6 flowing to the Tr Q6 is an offset current I0-I5, and this current is outputted from a Tr Q7 constituting a current mirror to the Tr Q6.</p> |
