| 摘要 |
PURPOSE:To improve the logarithmic characteristic by polygonal line approximation by constituting a circuit unit forming the logarithmic characteristic by polygonal line approximation by an IC circuit not including any capacitor so as to facilitate the multi-stage forming. CONSTITUTION:Plural number of full wave rectifier circuits having double balanced differential amplifier including the 1st differential amplifiers Qj01, Qj02, the 2nd differential amplifiers Qj03-Qj06 and the 3rd differential amplifiers Qj1-Qj2m, and adder circuits Q001, Q002 adding the non-inverting current of the full wave rectifier circuits are provided, the 1st differential amplifiers are connected in cascade, and the 3rd differential amplifiers are provided with the 1st TR pairs Qn1, Qn2 having nearly equal emitter size and the plural 2nd TR pairs Qn3, Qn4 connected in parallel with the 1st TR pairs and having different emitter size. An output current I0 of the circuit is expressed in equation. Thus, the logarithmic characteristic by polygonal line approximation of the 1st term and the logarithmic characteristic by polygonal line approximation of the 2nd term are cancelled at a point where the approximation of the logarithmic characteristic is not lost so as to improve the linearity of the logarithmic characteristic. |
