| 摘要 |
<p>PURPOSE:To prevent unstable operation immediately after turning on a power supply by disabling a variable electronic impedance device from feedback operation substantially immediately after turning on the power supply. CONSTITUTION:Immediately after supplying a power supply voltage Vcc to No.5 terminal, the reference voltage VREF of No.7 terminal flows to a condenser C2 through a resistance R27 and does not rise to 1/2 Vcc. Accordingly, a transistor Q9 becomes off-state, and current does not flow through No.5 terminal No.3 terminal switch Sn resistance R11...R1n GND. That is, as the transistor Q9 is in off-state, transistors Q3, Q4 of a variable gain current amplifier 4 become a nonactive state, and even when current flowing in the transistor Q1 or Q2 changes, the change of current in one transistor is not fed back to the other. When the reference voltage VREF rises nearly to 1/2 Vcc, a transistor Q13 turns off and the transistor Q9 turns on, and the electronic impedance device EID becomes a state capable of normal operation.</p> |
