| 摘要 |
PURPOSE:To reduce the generation of a VCO frequency AGC drift characteristic deficiency, by determining a differential voltage correlative with a forward current of a gain control diode of a video intermediate frequency (VIF) amplifier using a DC characteristic measuring method. CONSTITUTION:A PLL synchronous detection type semiconductor integrated circuit device 11 for VIF which contains a VIF amplifier built by connecting differential amplification steps 12, 13 and 14 respectively with gain control diodes D11 and D12, D21 and D22, and D31 and D32 is to be inspected. First and second DC voltages different in the level are applied to external terminals 15 and 16 for VIF input and each pair of transistors Q11 and Q12, Q21 and Q22, and Q31 and Q32 at the differential amplification steps 12-14 is turned ON at one end is turned OFF at the other end. With such an arrangement, first and second output voltages corresponding to the DC voltages are measured at external terminals 17 and 18 connected to collector terminals of the transistors Q31 and Q32 at the final differential amplification step 14 to obtain a differential voltage thereof. The VCO frequency drift characteristic of the device 11 is inspected from the correlationship between the VCO frequency drift characteristic thereof 11 and the differential voltage. |
