| 摘要 |
PURPOSE:To attain the multistage connection without using any clamping circuit, by including a gain control circuit in a feedback loop of a negative feedback amplifier and applying a 100% negative feedback. CONSTITUTION:A gain control part comprises the transistors TR202-TR209, and an amplifier consists of the TR213-TR218 respectively. When the control voltage input 212 is higher than the reference voltage VREF, the video signal supplied through a signal input terminal 201 is extracted out of each collector of the TR206 and TR209 since these transistors are turned on. The video signal is then supplied to the bases of the TR213 and TR214 to be amplified. This amplified video signal has a voltage follower operation since a 100% negative feedback is applied to the base of the TR203 from the emitter of the TR218. As a result, the base potentials of the TR202 and TR203 have the coincidence with an error corresponding to 1/(number of loop gain) of the amplifier. Thus the equal potential is obtained between the terminal 201 and an output terminal 220, and the longitudinal connection is possible for a gain control circuit without using any clamping circuit. |
