| 摘要 |
<p>PURPOSE:To eliminate a variation caused with temperature, and to execute detection from a small signal input level to a large signal input level, by forming a rectifying circuit for detecting an AC signal level by combining plural differential amplifiers. CONSTITUTION:An output signal V1 is obtained by amplifying an input signal VIN by the first differential amplifier consisting of transistors Q1, Q2, resistances R1-R3, and a constant-current source I0. Subsequently, V1 is inputted, and the second differential amplifier consisting of Q3 and Q4, and the third differential amplifier consisting of Q5 and Q6, whose output becomes an opposite phase to said amplifier are operated. Also, VIN is inputted to the base, the fourth differential amplifier consisting of Q11, Q12, Q13, Q14, etc. and constant-current sources I1, I2, etc. is operated, a current mirror circuit consisting of Q7 and Q8 is used as a load, and a DC current roughly proportional to a logarithmic value of a level of the input signal is obtained. Accordingly, small signal - large signal levels are operated, and a rectifying circuit having good temperature characteristics can be obtained.</p> |
