Voltage Controlled Variable Gain Video Amplifier

This is a video amplifier circuit featured with controllable variable gain.  The control is done by adjusting the voltage of grid inputs of two FETs, which are configured as programmable voltage divider. This circuit can generate dynamic linear range attenuation up to 100 dB. This circuit still give a linear attenuation even at f=10.7MHz.  You can see the control is done by a potentiometer, but you can replace with any voltage source ranging from zero to -10V, just make sure each of the two FETs is fed with different synchronized voltages. How to make this two synchronized voltages is described as follow: the first FET is fed with U1, which ranges from 0 to -10 V, and the second FET is controlled by U2, which is synchronized as (-10 – U1) V.  This control voltages can be obtained from DAC (digital-to-analog converter) or a stereo potentiometer (as depicted in the diagram). You can see a grounded 0.001 uF capacitor  to filter the control voltage from any glitch caused by dirty or bad potentiometer. Here is the schematic diagram of the circuit: