| 摘要 |
PURPOSE:To prevent the change of a video signal output due to temperature and the dispersion in a contrast adjusting function, by making the gain adjustment indirectly, that is, in the way of DC level. CONSTITUTION:The base of the 1st transistor (TR)11 is connected to a variable DC voltage source and the collector is connected to a power supply terminal 8 via a resistor 16. The base of the 2nd TR12 is connected to a fixed DC voltage source 18 and the collector is connected to the 1st TR11. At least one of the 3rd TRs 13-15 is provided, the collector is connected to a power supply terminal 8 and the emitters are commonly connected. A differential amplifier is composed of the TRs 11-15. The 4th TR9 is provided between the common connecting point of said emitter and ground of the differential amplifier, and the base is taken as a signal input terminal 4 and the collector is provided with an output terminal 5. |
